The west side is more commercialized, so that will be your better bet for a FHU site. The KOA is nice, but expensive. Decent amount of spacing but from what I remember driving thru, not a lot of trees. If your grandson is verbal, somewhat social and can tolerate others, then it would probably be best.
It took two short trips with my step-son who has Asperger's to decide that camping wasn't his thing. After about 3 hours, his attitude would kick in and ruin it for the rest of us. Worked out for all that he doesn't go anymore.