HI Heather! I am not certain when your family plans to travel to Walt Disney World Resort for your first vacation, however, if it is after June 24th, then, I would suggest opening night tickets to "Cars 2" and letting then know about your trip right after the movie finishes - as the credits roll. My kids would love it!
For your first visit to Walt Disney World Resort, I would recommend that you visit Magic Kingdom Park as a "must do". Children our kids ages will have plenty attractions to enjoy at Magic Kingdom and the Parades and Fireworks are awesome!
Heather, I would suggest that you look at your budget and determine which level of accommodations would be better for your vacation. The Disney Resort hotels are very well themed and you will be pleased with whichever Resort hotel you choose.
www.disneyworld.com under "Places to Stay" is a great place to begin searching for the Resort hotel that your family would enjoy most.
Have a Magical Vacation!