I would tend to stay close to Disneyland if that is the reason for the trip. You will be tired every long day and the closer the better. Close by should have a shuttle. Go ahead and take a day trip to Huntington Beach or
South Coast Plaza for shopping.
There are no RV resort type RV parks anywhere in LA/OC that I know of. At least not close to Disney. Even
Newport Dunes you are very wedged in and I believe it is close to $200 per night.
Beach may seem close but if you want an early start it is easily a one hour commute in traffic to Disney. Same for getting back unless you stay until Disney closes.
You said one day but two to four days is more realistic IMO. Then move and have a few days at the beach.
