I would stay at Diamond Lake. Much prettier and if you can reserve a spot with a lake view it'll be worth it. It's only a 15 20 min drive into the park from Diamond lake.
If you like to bike ride there's a really nice 12 mile paved loop around Diamond lake lake. If you like canoeing or kayaking the lake is fantastic for that. If you like hiking , there's several good hikes at Crater Lake and Diamond lake. I would do the boat ride at Crater lake. It's a different world down on the lake. Go in August as the mosquitoes are terrible in June, and just start tapering off at the end of July.
