I'm anxious to see the new pool at the Marriott Orlando World center (we may stay at Sabal Palms over spring break, got an owner's discount booked for now). But, for younger kids, I would look into Marriott's Harbour Lake - they have a great water play area for young kids! Plus, it's gated and safe feeling, and a small resort so it's easy to get around (I love it there, our rooms were always super clean and nice and quiet). Plus, if you get a one bedroom or larger, you'd have your own washer/dryer, so you can do any laundry before you leave. They have pizza delivery from Cypress Harbor across the street, and sandwiches also down at the bar area.
I'm sure there are many other options too; good luck, and happy planning!