Great question! Last fall I moved to South Davis County from a perennially sunny part of the country. Whew, it was a long winter with my kids! There seemed to be lots of active indoor activities in either SLC or Layton/Ogden, but not much in the middle. I found myself going to McDonalds two days/week so they could play on the play structure. And spending $10-18/visit on fast food! That's desperate, in my opinion!
I was thrilled when Kangaroo Zoo opened in early April in NSL (they already had a Pleasant Grove location). We held a birthday party there with kids from 14 to 1 and everyone had a great time. We have been back several times since. Oh, and they even have indoor, glow-in-the-dark miniature golf! See KangarooZoo.net.