This group site consists of sites 10, 11, and 12 of the Chatter Creek Campground. All together, it easily has enough room for 45 people, as stated on recreation.gov (where it can be reserved). When you pull into the campground, there is a Y: right takes you around the camp loop, left takes you past a gate to the group sites. There are 2 vault toilets, a dumpster, and potable water near the "Y."
The sites are lovely! There are rocks and logs to climb on, a rushing creek, and plenty of downed trees for firewood. The shelter at site 11 has a fireplace and an area to prep and serve food. All 3 sites have connecting trails.
Well worth the drive, although once the pavement ends right before Ida Creek and the road gets very rough. I made it up in a full-sized car, although I did scrape bottom a few times.