My then 10-year old son took that redeye last year to meet me in Orlando ( I was there on a business trip ). He did great - he was so excited we made it till 11pm that night on adrenline! We were able to make the rope drop at AK, which was great - headed straight for Everest - grabbed a fast pass and got in line so rode it 2x right away. That'll wake anyone up!
Bring a pillow for each flyer - those little plush neck ones they have at Target are fine and don't take up much room. Every inflatable I've tried leaks - so I wouldn't bother with those ( even though they pack flat). The airline pillows are pathetic - but if they offer them, take that as well. I've never been hassled about having a pillow at the top of my "personal item" bag. The earlier you board ( since you have smaller children, you may be able to take advantage of that ) the better the chance of getting a pillow and blanket - they don't have 1 for everybody!
It's much easier to sleep against a window - but I'm sure you want to sit together. Raise the arm between the seats so you can snuggle ( seems obvious, but I sure didn't know it the first time I flew).
Wear SUPER comfy clothes - don't worry about what you look like! But bring clothes to change into at the airport or the hotel restrooms ( the really nice hotels like the Grand Floridian have beautiful public restrooms with roomy stalls). And of course a toothbrush and other personal grooming items. And the swimsuit idea is a good one.
There were relatively inexpensive smoothies with energy shots at the airport - I got my son one of those to give him a good start.
Make sure you take full advantage of your carry-on luggage. Make sure your carry-on fits the size requirements, and keep your weight under the max - I've seen many people charged $50 for being overweight on their checked bags. Don't forget to leave room for what you'll be buying. Check out the long thread on packing -- it's a good one. But: watch that weight!
I pack my normal purse inside a BIG purse as my personal item. Then it can fit lots of important stuff. Always allow for the fact that a checked bag may be lost - so valuables like cameras, prescriptions, etc should be in the carryons. I count the bags everytime I get on/off a plane to make sure I've got everything - including the backpacks, etc.
And then base the pace on your kids. There's always the Carousel of Progress for a good 20 minute nap! ( kidding - I LOVE that and always go on it -- miss having it at
Disneyland )
Have a great time! I'm going in June with my kids and granddaughter- couldn't get the redeye out because my daughter-in-law was too timid to try it with her 5 year old, so burning up a whole day travelling. I'm jealous!