Seattle to Anaheim and back

I'm planning a 9ish night road trip from Seattle to Anaheim and back in Mid-September. We will probably spend two days at Disney. The person I'm going with wants to do lots of stuff on the beach as well. We're planning on camping to save money (thats feasible in September, right?) and then going up the east coast through Yosemite and back. It looks like stops in Crescent City, San Francisco and Anaheim and a day in LA. We're budgeting 3-4 days to get back.

Anyone know of any good campgrounds along our route that are open in September? and Are our plans realistic?