This is about Cottonwood Campground, not just the group site. It's pretty small, about 16 (?) sites. It's about 8 miles up the road from Hwy 89. The road is mostly one lane, though a little wider in some spots, so if you are towing, hope you don't encounter someone coming the other direction. There are some potholes all along the road, so if you're towing, it's slow going.
The campground is about 1/4 mile or less from the lake. Group camp is up the right hand fork (not towards the lake). The Group site is large, with room for several tents. When I was there a church group of about 18 people with 5-6 tents was there. The sign says it requires reservations. There are 2 pull through sites up the right hand fork; the rest are back in or walk in. The walk in sites do not have tent pads or even room for a tent so I'm not sure what you would do there. The left fork goes to an equestrian area with a couple of non-equestrian sites also.
Each site has a picnic table and fire ring. I collected a lot of trash from fires rings.
There were vault toilets that were very clean to start with, though a camper pooped on seat in one of them, so gross. I don't know why people are so filthy sometimes.
There are trailheads from the CG and from the south end of the lake.
No signal on Verizon.
I enjoyed staying here.