Sounds like you are doing a similar family trip we did back in 2007.
Glacier CG is a nice place on the west side of the park. We spent 5 nights there, wish we could have had more.
Obviously, the Going to the Sun road is a must. Truly spectacular. There's a few white water river outfitters up by West Glacier, and the rapids are not severe...no danger to your 5 year old, the kids would love it. The Flat Head area, a little southwest of there has some nice scenic drives. Check out the town of Kalispell & Whitefish too.
When we left Glacier, we tookUS 12 across Idaho towards McCall, and camped at a nice place near Riggins (Canyon Pines, I think) right on the river. Beautiful spot, near the Seven Devils Mtn. range.
When we went to Yellowstone (after Glacier), we stayed on the Idaho side near Driggs. Can't recall the name of the CG, but the Tetons weren't too far away, neither was Old Faithful and the Fire River.
