We are members of the Minnesota Zoo. It's just a great place to go, year-round. Aside from being a destination with great exhibits and learning opportunities on a normal visiting day, they also offer great kid and family programs. We have not had a chance to participate yet, but I do have a friend who has. She and her family did a zoo encounter with the bears, who are some of the zoo's most popular residents.
For kids and families, they have classes, tours, camps, and overnights for almost all ages (all the way down to 2 years old), as well as career exploration and conservation seminars all the way through 12th grade.
On their "Games and Activities" page, they have online games you can play before your visit as well as crafts and a scavenger hunt.