Im with PCskier on Deer Valley. My kids have been in their locals program for a few years, since they were 3 & 4 (six Saturdays, all day+ lift& lunch, under $500) and it's been outstanding. Before that, the daycare, even for infants , was outstanding. I think people can have negative experiences anywhere, and nobody's perfect- but these guys are everything that Pcskier says they are. And on presidents week, they find even more patient, cheerful, attentive young instructors to handle the extra kids and everybody's happy. Even my houseguest's moody big city kid...
Joey, my three year old daughter (now four) had a small class- not a lot of students that young- and on many Saturdays last season I spotted her in a wedge right behind a terriffic 20 year old kid skiing in a backwards wedge, leaning down and chatting with her... one on one. So say what you will, but DV is the gold standard, and that's that. For day care, and if you got a kid in diapers, DV is the only place, IMHO.
Alta ski School is great, especially for the terrain, and they have wonderful people.
Sundance is wonderful too, with it's easy lower mountain, small resort relaxed atmosphere, and earnest, cheerful, "well scrubbed" staff, mostly from BYU.
I've posted before that of the resorts I spend a lot of time at, DV and Alta have large areas that are beginner only, without knuckelheads maching through to get back to the lower lifts. Sundance is no danger because it's so uncrowded and the lower mountain is vast and pretty flat. (no bottlenecks) I'm not very familiar with Canyons, Solitude, Brighton or Snowbasin. Snowbird has a good rep. No personal experience, though. The Adult school is killer, I can attest.
PCMR is hosting a new Friday kids program for our school so my 8 year old will be in that- I'll make a full report come February.