Fruita Campground is now reservable on recreation.gov. There are only a few sites that are open first come first serve. That said, yes you can put a tent and rv on any site that accommodates them as long as you have less than 8 people total.
There are spots that would accommodate that, spots fill up fast and it's first come first serve... So get there early. Someone in my group usually drives down the night before so they can find the spots that work for our group and grabs it as soon as possible.
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