Driving out to the dunes, there were people using little boards to try and ride down the dunes. Not sure how successful they were. ;) There is a nice, shaded path along the pond at the end of the park where the picnic shelter is. Beyond the shade, the sand was too hot for our dogs paws so we turned back.
There was a family celebrating a birthday in the large shaded picnic shelter. The kids were wading in a small inlet.
In addition to being a nice day trip spot, there are two campgrounds for longer stays.
Great place right off the road for a night or more. River is right behind your paved site and wide green spaces between. Host were very friendly along with Park Ranger. $10. a night, no hookups but water at many places in park. Clean bathrooms and showers, a bit noisy during the day but not at night as highway traffic slows or inside the RV.
I haven't been into the campground. We have been using the picnic area to get to the Grande Ronde River. Didn't see a bathroom by the picnic areas but maybe one in campground
They have campsites that cost money, and in the evening time they lock you in. That being said, the grounds are spectacular and you could come to the front part of the park where there is no fee and just enjoy swimming under the bridge, waiting in the water are just sitting underneath the trees enjoying nature. I played guitar there I felt at ease there. It's a beautiful state park and if you have the chance you should visit it.