Although Bergen Science Centre (VilVite) isn't listed under "Children's Highlights" in the Lonely Planet guidebook, it should be.
There are plenty of interactive games for us to spend a full day with two eight-year-old kids. Of course, remember that you can pop in and pop out for one whole day, as long as you have paid for the entrance ticket.
An additional (unexpected) activity for us is finding an open area just outside Bergen Science Centre and, hurray, free time in the playground. My daughter quickly came to see the opportunities to play tag (which, I strongly believe, is itself an inherently good thing to do, besides learning science).More