We like Gull Point Campground, reserving a spot on the Deschutes side so we can beach our boat by camp, however, it is probably too late to get those spots reserved this close to Memorial Day. I think Gull Point has several first come first serve spots, but they are not on the water.
There is also a RV park on the Deschutes arm near S. Twin, not sure of the name.
There is an RV SITE at twin Lake with power hook up and you can moore your boat on the beach 541 382 6432 you motor up about 2 miles from the main lake. they are book for the holiday. The Main lake is Gull point camp grounds they take some spot for reservations and some are first come first serve you can moore your boat on the beach at any spot/like DLM advise some are just futher than others I was lucky enough to make a reservation at Gull Point been calling for a cancellation at RV site for a power hook up but no luck I'll also be up there for the memorial Holiday/its a very camping friendly lake.
I was there yesterday. The water level is high and some campsites are not accessable at Gull Point due to flooding. You can go online to reserve a spot, or take a chance at one of the first come, first served sites. I'd try to reserve.
If not, about 2 miles down the road is South Twin lake. Across the street is a big campground and you might have a shot there.
Will be there the first week of June got space 36, haven't camped there yet myself hopefully it is not flooded and can keep an eye on the boat if able to pull it up on the bank. Thanks KK