If you are very polite and$ lucky at checkin, perhaps they will block off an extra seat for you.
I feel for you, this is the most difficult age for flying (have been there many times).
See if you can get your little one used to wearing headphones before the trip, otherwise the inflight entertainment system may not be much use. My kids couldn't use them till they were older as they were too big for their heads! Perhaps bring yor own ear-bud style if they will work on the plane.
Very simple crafts for kids too young to draw.
- Stickers. Most toddlers can peel and stick stickers. Prepare ahead things to be decorated eg, cut out a circle from card, and punch out a hole near side. Child decorates with stickers or whatever, then thread hole with some thin ribbon, tie and wear as a medal or pendant. Similarly, cut out a spikey topped crown shape which can be decorated, ends stapled together and worn (small staplers ok on planes). Spin out these activities by doing one for you and one for doll or teddy. Pack each activity in a seperate ziplock sandwich bag.
- Threading or lacing activity
- New inexpensive toys for imaginative play eg cars, dolls, farm animals. Don't forget the accessories.
- Paint their fingernails
- Pop bubblewrap
- Finger puppets (ikea has cheap ones)
- Try "panquil" available over the counter from pharmacies. Makes them sleepy, but test at home first.
- Last ditch emergency item - favourite forbidden food (for my kids, smarties, kept concealed)- to defuse either a tantrum or nervous collapse by parent (nine times out of ten I didn't use it, but really needed it when I did)
- Books
- lots of walks around plane