sd ranks his favorite times to go to WDW:
1. Late Sep/Early Oct - Kids back in school = very low crowds. Food and wine festival and Epcot. Still warm enough to do the water parks.
2. The Sat after Thanksgiving thru 7 days before Christmas. As noted above super low crowds. Cooler weather but sometimes still warm enough to hit the water parks. Was 85 when we went early December this year. Christmas lights, shows, special fireworks, etc.
3. Late April/Early May (One week after Easter to One week before Memorial day) - Depends where spring breaks fall which depends when Easter falls so track that. Can be hot. Hit 90 when we were there this time last year. Great for water parks. Good crowds (not as low as #1 and #2 above but low/medium). Flower and Garden festival at Epcot so it's pretty.
We usually stay at the Epcot resorts. Beach Club, Yacht Club, Boardwalk, Swan and Dolphin. Usually the Swan and Dolphin if we have enough SPG points. Staying at the Boardwalk this Dec. Yacht and Beach Club have the best pool. Swan and Dolphin have the best food and booze. Boardwalk has the best atmosphere imo. Have stayed at the Contemporary as well which would be a good option if you are mostly going to hit the Magic Kingdom.