ok, well, seems like most tips are pretty much covered here.
definately the #1 thing is to take it easy. i know it's your first time and, naturally, you're going to want to fit in as much as possible (even some of us who go annually try to fit in everything every time we go) just know that there's LOTS to do, and as someone mentioned earlier, try not to get overwhelmed. just take your time and have fun. if you don't get to do everything you want to do, that's just an excuse to go back
whoever mentioned taking a camera, that's a great tip! and, of course, if you have a video camera take that as well....i promise you, the memories you will make at WDW will be priceless!
PixiePower's right, interaction with cast members (WDW workers, in case you don't know) can make the trip even more magical! of course, now-a-days, there's a few more 'bad' CM's than there used to be, but for the most part you'll find them pleasant. oh, and while walking up Main Street in the Magic Kingdom, if you happen upon a certain fellow wearing a dark-reddish plaid suit, glasses, and hat and carrying a large brown leather bag with a jingling toy attached to it, talk to him! his name is Scoop Sanderson and he's the pin-trading guru on Main St. i'm telling you, he'll make your day! he's a real hoot! and he's super great with kids!
if you can, eat at Sci-Fi Dine-In Theater at MGM Studios. you don't even have to get a whole meal. my family and i have gone in there before just for chocolate milkshakes (which are WONDERFUL, btw) depending on how busy the park is, you might need reservations; but if it's slow you might can get away with just walking in during a typical non-meal time (before lunch, between lunch and dinner)
if you have time, try to take in Downtown Disney. i'm sure your kids would love the DTD Marketplace stores...World of Disney is the largest store on Disney property and Once Upon a Toy is fairly new and has some Disney World exclusive toys.
and if you want a good spot for parades and/or fireworks, find a spot at least 30 min. in advance. just for good measure, you might want to ask a CM about good spots for such events. btw, i HIGHLY recommend seeing SpectroMagic (Magic Kingdom's nighttime parade) Wishes (MK's firework display...try to find a spot where you're looking straight on at the castle) and Illuminations: Reflections of Earth (Epcot's firework display...try to find a spot with an unobstructed view of the middle of the lake)
Mickey's Philharmagic is brand new and a great show for the whole family...definately add that to your list.
if Carousel of Progress in Tomorrowland is open, see it! it was the first attraction Walt created and is definately a classic! unfortunately, it's gone seasonal, so it's a hit-and-miss sort of thing.
i think that's about all i wanted to touch on. welcome to the boards and have a magical trip!! and come post a full report when you get back home! :wave: