Go to the Disney waterparks rather than Wet and Wild. My memory of W&W is that it was tatty but they may have done it up since then.
MGM studios has Playhouse Disney live on stage (Bear inthe BBHouse, Roley Poley Oley. Pooh Bear...) which DSs (4.5 and 2.5 at the time) throughly enjoyed.
Also, the character dining buffet in the Crystal Palace in the Magic Kingdon was fantastic. It was Pooh Bear and friends when we went. DSs were sooo excited, the food was as much as you could eat and was superb. It wasn't exactly cheap but it was good value for the excitement and the quality of the food. Book a slot in advance when you arrive at the park.
Trying to think of restaurants... Most are very child friendly and cheap to be honest. Breakfast out is wonderful - best bit of an American holiday for me!! Look out for the free visitors guides which are in those newspaper dispenser type things all over the place. They have vouchers for special offers etc and can give you a good idea.
If you want maps of the theme parks in advance to plan your trip, email me on huffhorse at hotmail dot com and I'll send you some of the hundreds we seem to pick up in October last year!
Another top tip : FASTPASS! The more popular Disney rides have a system where you insert your park ticket and you are given another ticket to bring back to the ride at a specified time later on (usually an hour slot about 2 hours or so later). You can then skip the queues and go straight to the front. Essential with small children who don't want to wait in line.
Do NOT go on "It's a Small World" inthe Magic Kingdom. It's horrid, horrid, sickly and horrid and you'll be singing the song for the rest of your life
DSs loved the 3D shows. Mickey's Philarmagic and It's a Bugs Life (Animal Kingdom)were favourites.
Take water with you although there are fountains throughout the Disney parks (the water from these tasted metallic to me). Also agree with taking snacks to the park.
Check the times for Character Greetings where you can have your photo taken with assorted Disney characters.
Look out on the maps for the play areas. These are a nice breather from the hassle of rushing round the rides and stuff.
Even though it's October, don't forget hats and sunscreen! There can be very little shade in places.
Will you be in Disney for Halloween? If so, you could book for Mickey's Not-So-Scarey Halloween party which (I think) is in the Magic Kingdom after the park has shut. I'm disappointed that we didn't know about this far enough in advance.
Flying - lots of small snacks, cheap toys and sticker/colouring books. DS1 did, however, watch some cartoon about a horse on a continuous loop during one flight with Virgin to the US. You'll probably find there'll be something to amuse them on the seatback TV. There's not much in the Virgin satchels TBH so don't rely on them for amusement value.
Oh... I want to go back!! We're not going to the US this year