First off -- You're going to have an awesome time .. I guarantee it.
And if you're not.. just look me up -- I'm stayin at Pop the same week as you!

How cool is that?
Seriously - I've been many times. I tend to avoid the pricey stuff.. it means I can go more than 1x a year if I'm careful with my money while I'm there.
I eat counter service meals for most of the trip and have one or two 'nice' table service meals. Last time we ate at Wolfgang Pucks in Downtown Disney and it was a great meal for a fair price I thought.
Now.. with that warning.. I don't have kids.. So if yours are picky eaters, they might not like Mr. Puck's restaurant. I dunno.
The refillable mugs at the Pop resort were great. Frozen Coke, most any soda, a good selection of ice teas, juice, coffee .. whatever. I drank a lot of Coke last time with mine.. my buddy who came with drank lots of apple juice with his. Go figure.
The stuff I find that
"sucks up" the money faster than anything at Disney is the following:
- Souvenirs : We always do the same thing.. if we're going to get any, we wait and get them on the last day and usually at Downtown Disney's World of
Disney store. I tend to buy one or two things to bring back for friends. I don't need any more Disney stuff myself!
- Meals : Careful decisions about where to eat can save you some dough. Take a few minutes and check over the menus of the various restaurants throughout the parks online. AllEars has a great selection of the menus as does this site (wdwinfo.com) - Even the counter service meals are WAY too pricey to order something and decide you don't like it at all and waste it. So.. look ahead and figure some of the places with menus you can definitely find something you'll like. And read on the restaurants forum here on the DIS. EVERYBODY on here has their favorite places to eat at WDW and nobody seems shy about sharing their suggestions. LOTS of great ideas. Bonnie in the post before this one had some great money saving ideas. I've used those before! [ And thanks for the tip on Earl of Sandwich Bonnie - I'm going to TOTALLY check that out ]
- Photographs : Any of the 'on ride' photographs -- while cute as heck and a great keepsake.. they are pricey. If I absolutely MUST get one.. I get JUST one each trip. I don't bother with one for each ride.
- Snacks : I list this separately because lots of times I'll be cruising around the parks and they'll have 'snacks' that are just TOO tempting. I try to limit myself to one snack each day. Other wise a turkey leg, a churro (its like a doughnut but long and skinny), an ice cream bar... and a couple of drinks throughout the day adds up VERY fast. Plus, I'd gain weight like CRAZY if I ate all the stuff I wanted there.
And one other great idea is to check out the "BUDGET BOARD" here on these forums. They have some amazing ideas for how to cut costs without cutting corners or lessening your experience. I go there ALL the time for great ideas to keep my costs low.
Hopefully some of this will be helpful.
As for the Magical Express thing, I would call and ask Central Reservations (or whoever booked your trip) if they can help you out with that. I'm surprised they didn't do it for you when you booked.
Have a FANTASTIC trip.. The kids will love it.. and I bet you adults will feel like kids at times too. I do.. everytime I go!
John