I went this year in February and May (February with DS and DH, May as a solo). I wasn't around holidays either time and I must say I prefer February much more because of the weather. It was very chilly at night, but nothing a heavier sweater couldn't handle (I am a native Floridian, so cold is not something I'm used to). During the mornings we wore light sweaters or sweatshirts and could change into tee's for the afternoon. I think the high during the time we were there in mid-February was 70 with the lows at night in the 40's. It was wonderful. The lines weren't bad and even if you had to wait it wasn't terrible because you weren't sweating. We hit all the parks early and hopped - a lot. In May the crowds were heavier, although still manageable, but the heat was already getting bad. I had to leave AK early one day since the high was 97 and I almost passed out. I'd say February is the ideal time to go, you just have to bring more of a variety of clothes.
As for the resort...depends on what you can afford and what you're looking for. They're all so different.