Hi Heather,
I love first trips! However, I know how overwhelming a vacation at the Walt Disney World Resort can be!
You will need to look at the villas to find three bedrooms. These are located throughout the property and allow guests privacy as well as full kitchens, extra bathrooms and a washer/dryer unit to use.
Depending if you plan on coming back and forth during the day for naps and breaks, this will determine which resort will work best. My first recommendation would be for Bay Lake Towers by Magic Kingdom. The Beach Club or Boardwalk by Epcot and Disney's Hollywood Studios are good choices as well because you can walk or take a boat to both parks. I also like their pool area better than Bay Lake Towers.
Once you decide on a resort, then look to plan your schedule and dining. You do not need park hoppers as you should spend one day at each park to experience all its magic.
Wishing you a magical first vacation!
Beth