The Twin Cities is full of stuff to do - it all depends on what you are interested in. I would recommend the Science Museum, the Minnesota Zoo and the Minneapolis Institute of Art for museums.
If you like music there are all kinds of options once summer gets here. Lots of festivals and music in the many parks.
Of course there are lots of parks and lakes if you enjoy the great outdoors. I have a website that is geared toward families, but you might find it helpful for the list of attractions and events. www.thingstodowithkidsmn.com/