Welcome BACK, Denise!
How exciting that you're planning a trip back Home to Walt Disney World Resort next year. And I love that you're bringing your niece to share in all of the fun! Walt Disney World Resort has done an incredible job at offering a variety of Resort Hotels that can accommodate all kinds of travel party sizes and budgets. I completely understand the need for more beds to fit the sleeping arrangement for your extended family of four. A little trick that I used for this answer was to view all of
Disney's Resort Hotels individually, and I looked for the rooms said 'Sleep up to 5 Adults'; each room maxes out at two bodies per full, queen or king size bed, so a room that 'sleeps five' will have at least three individual sleep spaces.
The Standard, non-themed rooms at both Disney's Caribbean Beach Resort and Disney's Port Orleans Resort - Riverside feature two Queen-sized beds + a "Child-Sized" pull-down bed. I stayed in one of these rooms at Riverside in May, and for resEARch reasons I tried out the smaller bed. I'm 5'5" (and a half) and while I did take up the entire length, I would have been fine sleeping there the whole trip.
For rooms with more space as well as beds, look into the Family Suites at both Disney's All-Star Music Resort as well as Disney's Art of Animation Resort. Each feature three individual beds, and as a bonus there are two bathrooms.
Three Resort Hotels have rooms that feature bunk beds: Disney's Animal Kingdom Lodge, Disney's Wilderness Lodge and The Cabins at Disney's Fort Wilderness Resort.
And most standard rooms at all of
Disney's Deluxe Resort Hotels can sleep five, thanks to two Queen-sized beds and a couch Day Bed.
I hope this helped, Denise, and We'll See You in 2019!
~Kristen