I'm late to the discussion, but might share some of our experience. Back in the late nineties we travelled back and forward to the US with our then two daughters starting when they were 18 months and 3 years (now 20 and 22). I was working in San Jose for 6 weeks at a time and then come home for a similar time. Did this for a few years until eldest was starting school. We got quite good at it, although the flights themselves were never what you would call fun. We got very good at packing and would even haul child car seats backwards and forwards.
All travel was in Y as my employer would allow me to spend whatever I liked on economy flights up to the value of my normal business class fare. We would normally get 4 economy fares (no, we wouldn't go 18+ hours with a child on a lap - I wasn't that cheap), plus internal US flights for a week or two's holiday at the beginning or end of the San Jose stint for less than the then single business class fare. It was before the days of skyscanner and the various other flight search sites, but I did have direct access to the Sabre system (dumb terminal via a web browser - had to learn all the travel agent line command codes) so I could see flight inventory and bargain fares. With the judicious use of consolidator fares we did quite well I think. I would send the fare and routing codes to my employers travel agent and they would book the flights. Travel agent wasn't happy as the commissions were less than what they offered, but my employer was a big account, so they didn't argue too much.
Typical routing for us was BNE-SYD-LAX-SJO/SFO, with total travel time including transfers of more than 24 hours. Wife's brother was in Washington DC at the time, so the other common routing was BNE-SYD-LAX-Saint Louis-Washington National, with total travel time of more than 30 hours (best case assuming that the TWA legs from LAX to Washington didn't encounter some problem which they invariably did). IFE wasn't flash in those days or non-existant on the cheap TWA flights.
A few comments on previous posts. Yes, we did try Phenergan, but in our case our eighteen month old spewed it straight back up. Thankyou to the Air NZ cabin crew who helped us out replacing all the seat cushioning inflight. So yes, try this before you need to use it in anger. I have heard of people using it to get the child accustomed to their new time zone. On the IFE height/viewing angles, yes this is a problem for little ones, and you really don't want them sitting on pillows etc. I'm having the IFE viewing angle issue my self now that I wear multi-focals and I'm not particularly tall. I now take ordinary reading glasses on any long flights so I can use the IFE. Toys with parts are good, but you need to strike a balance. You don't want to be crawling around the floor finding that missing part. We did have a variation on the Velcro idea that worked well. It was a fabric book that zipped closed. All the book characters were little soft dolls that could be velcroed in place or played with like puppets. There were various other moving parts like toothbrushes and combs. All the characters and bits and pieces were connected to the book spine by warn or string.
In general, most fellow PAX are generous and understanding of your predicament, even if your child is upset or cranky, if they can see you are making a bit of an effort. Food/snacks works, but nothing too sugary or red. Book seats so that the child is not running between you. Aim for two aisle access as you will be getting up a lot. Don't pull on the headrest in front when you are getting up.
Now, onto my suggestions. All the ideas like IPADS, IFE etc are all good. You need as many weapons in your armoury as possible, but the point I'd like to make is that these things tend towards either the very active (eg: IPAD games) to the very passive (eg: watching cartoons on IFE). These comments are just opinion - don't flame me! We found that something in the middle worked best for us. Something that needed a bit of pre-planning and effort, but definitely low tech. Something that was familiar and comforting, and that needed some involvement by the child without too much. We did our version of talking books. Most kids this age have a number of favourite books and they want you to read them repeatedly. We would record us reading the books (on a tape Walkman in those pre IPOD days, but you could easily create MP3s on your laptop now) ringing a little bell to turn the page. The child knows the story, so if they lose their place they can normally find the right pictures themselves without bothering you. They have to be engaged enpough to follow along, but they don't get hyped up. Yes, you can get commercial read along books, but there is something comforting about Mum/Dad/Grandma/Grandpa reading to them. Maybe you can con Grandma/Grandpa/Uncle/Aunty to do it as a going away gift. The actors on the commercial versions tend to be a bit dramatic.
YMMV may vary, but it worked for us with our three girls. I've also used it quite successfully with nephews, so I think it can work with boys as well. One find we did discover at the time were some tiny format books of popular titles like 'This is how much I love you' and 'Old Pig'. Titles are from memory, so may not be accurate. They were designed as an alternative to a birthday card and you could get them very cheap in the US. Cheap enough that if they got lost during a journey, it didn't matter. We bought a stack and would give them away as presents to any kids doing long trips. I tried to find one just now, to get the publisher, but I think we have given them all away. From memory, it was one of the greeting card companies.
Wow, this has been a bit of a diatribe! Thankyou for your patience and I hope you get some value from it.
Enjoy your trip, and even if something bad happens, you will be laughing about it in ten years. We had some shockers. The Phenergan incident. Arriving at Qantas checkin at BNE with prebooked seats (4 across the middle of 747) when the agent asked did we book 4 separate seats in four different parts of the plane on purpose. We had some polite but frustrating discussions with the Qantas load master in Sydney. His opinion was that they could reassign seats however they liked, which they can. Right up until the last minute his best offer was two seats together plus another elsewhere and the baby would have to travel on our lap for the next 15 hours despite buying a seat for her. As the doors were about to close I told him we would accept the four seats that Qantas had reassigned without our knowledge but the cabin crew would need to look after the children because we wouldn't be anywhere near them. To our amazement, he quickly was able to organise four sets together! There was also a Washington-St Louis-San Jose flight that took more than 24 hours. A storm front went through having us offloaded from the first leg just before takeoff, and when eventually reloaded and getting into St Louis too late for our connection. Joined the transfer desk queue with a couple of thousand other people. Eventually after many hours, they brought a spare plane out of a hangar, found a crew and had a special flight to try and clear the backlog. It was only about 1/4 full but it is still amazing how much stuff Americans can stuff in those overhead lockers. By this time the storm front had passed through St Louis, between us and our west coast destination, so the flight path took us up over Canada adding a few more hours to an already long flight in what was an MD-80 or MD-90. Cabin crew told us that the plane could only fly that long because of the low occupancy and a full fuel load. There was no food service at all, not even the brown paper bag with stale sandwich and packet of potato crisps you normally got as you boarded that flight. One of the cabin crew who had a bit of forethought, had filled up all her pockets with little packets of pretzels on her previous flight, so that was our cuisine for those 8 or so hours.
All the best!
