You could spend several days exploring there.

It would be fun to drive up to Hungry Horse Dam. They have a little visitor's center there that's cool. It's an impressive dam.

Whitefish Mountain Resort is an awesome place. I don't know what summer activities they have, but I imagine they have mountain biking, hiking, etc. Not sure if they have Alpine slides, but they might. It would be fun to just drive up there and see the houses up on the mountain and the view of the lake and surrounding mountains.