Stayed at Little Bitterroot Lake last year(Aug 2018) for 3 nights and had a great time.
After seeing the crowds closer to Kalispell, we enjoyed the slower pace of Little Bitterroot lake. Got a great site, where the tent literally opened to a beautiful view of the lake.
Nice clear lake for swimming or fishing for trout. All types of boating is allowed.
We saw many eagles fishing for dinner, and even a snake swimming in the lake.
Nice clean campground, well-maintained facilities, and they even have a dock and a playground! The lake is great for swimming and fishing.