My family and I just got back from visiting the Ice Castles in Stillwater MN. We had a blast!
When we first got there, it was somewhat smaller than I expected. However, as a family (myself, husband, and kids age seven and nine), we spent just over an hour there, and left satisfied - if a bit chilly. Although our tickets were comped, we definitely would have paid the price for the advance tickets (which I strongly recommend, as it's a significant savings over the walk-up pricing, plus it guarantees entry time if they're busy). They had a lot of fun little parts to the structure, include cute places to take pictures, slides (which my kids loved), a maze (which was easy, but still fun), and lots of little nooks and crannies my husband enjoyed photographing. (Check out his awesome work on Flickr.) You can tell that a lot of time goes into it - 4,000 hours shaping the ice and embedding with LED color-changing lights. The music that plays is appropriately wintery, and long enough that we didn't hear a song repeated enough to be annoyed.
The night we went, they had insphyre providing fire entertainment. It was mesmerizing, and after the performance they encouraged people in the crowd to come up and take pictures with the flaming wants before their warm-up break.
If you go, definitely dress warm. Walking on snow is cold - so be sure to wear layers. Saturdays and Sundays they have Tiny Diva Princess Party photo ops 12-5, and insphyre fire performance 6-9 Fridays and Saturdays. Parking is free on surface lots, and on Saturdays you can park at the high school and ride a shuttle every half hour. We didn't have a problem finding parking, but it was really cold tonight, and might be busier on a warmer day.