What's the budget for your son? Are you going to subsidise him a bit for this effort?
Looking at the rates on booking.com alone, I'm actually surprised prices haven't got out of hand yet. They aren't say really cheap, but given that it is so close to the date, these are actually good rates. Needless to say, if there are romance packages available (which I can't see on booking.com, you would have to go to other websites / the hotel's native websites), they'll be in high demand. Staff will be setting up many rooms on the 14th!
In response to
Solid and
Clivem, the Limes and Emporium hotels are amongst the most expensive on those two days. An alternative to the Limes is the Diamant, which is not as stylish looking but still quite understated and still more sophisticated than a standard mid-range hotel. The best room at the Diamant is going at a decent daily rate, about $230 per night. The Emporium appears to have a nice Valentines package in a spa suite for around $479 for a night - probably get one night with that package and another night at another rate.
In the CBD, the Pullman King George Square looks pretty good and the rate decent enough. This was looking at lastminute.com.au, and there appears to be a couple of other good ones.
The Hilton still has standard room awards as well as cash + points awards available. However, without status it may be a bland stay, though; e.g. no Executive lounge access, no complimentary breakfast, no free internet in the room......
