As a norwegian I should know these cities pretty well, but we tend to loose focus on the highlights in our own country.
Here's a list of things I find interesting:
Aalesund:
Walk the streets and feel the atmosphere of a cozy western norwegian town. I you were hikers and not so afraid of heights it is wonderful to climb the 480 something steps to the top of the town mountain Aksla.
Alta:
Have not been there since I was a small child, but I will be going there in the end of may. really don't know what to focus on here, but would guess it's a nice place to look at some craft made by the laps and their culture.
Tromso:
The polar cathedral (ishavskatedralen)
Polaria: Polar museum with the story of the arctic and a seal aquarium
Molde:
As you suggest the folk museum.
Bergen:
A LOT

Suggest you find a good brochure and pick what interest you the most. A must do is the fish market and the Hansa area with the piers. Again the height issue: There is a steep tram line to a mountain called Floyen which would give you a terrific panorama over the city.
In Nordnes there is an aquarium and a nice little park.
Have a wonderful time in Norway. I hope the weather will be on your side.