If all of the campsites have already been reserved inside the park for the day that you want to go, are there some good places for a group of about 8 people to camp near the sand dunes?

Great, thank you so much for the suggestions everyone! looking forward to seeing the sand dunes in person :)

You could also try Zappata falls about 7 miles down the road from Sand Dunes

I think a lot of places are booked up, but try the sand dunes pool. Or if you can go without hookups, the ufo watchtower always has space. She is a nice (and mildly kookie) lady and will let you set up on her land even if her actual spots are full

What Shane said👇👇

Yes, just outside the gate is the Sand Dunes Oasis. Their regular campsites are first come first serve and they have larger group sites and RV sites that can be reserved. They have flushing toilets, showers a store and a restaurant.