We very much enjoyed Craters of the Moon back in 2010. If you go, Indian Tunnel is IMO the best lava tube. If you walk to the end, you can climb out a small opening and then walk back across the lava flow. There are two private campgrounds in Arco if you don't fit in the Lave Flow CG.
X2 on don't drive route 22 over the Teton Pass. Route 26 is longer, but no white knuckles.
We have used route 89 from Brigham City to Jackson twice on past trips. An enjoyable drive with great scenery.
If you want to head up to Grand Teton early, you could stay for a few nights at the Gros Ventre CG (our favorite) in the southern end of the Park. We arrived there on June 4th last year and there were only 20-30 sites in use at that time. You should have no trouble finding a site that would fit your rig. Dry camping, but they have water at the dump station. Watch for Moose along the river south of the campground.
IMO, it's impossible to spend too much time in the Tetons.
