We did a PGL family break at Barton Hall about ten years ago, along with a single mum friend and her two boys. Five kids in all, between 8 and 13.
I can honestly say it was the most fun (and possibly cheapest) holiday we ever had! Everything was planned out, so we didn't need to think about what to do today, and the activities were amazing. No opportunities to spend money, either, which kept the costs low. It was so fun to let your hair down and do things like trampolining, leap of faith, high ropes and quad biking, that are usually left for the kids. Some of it was actually quite challenging - my 8yo DD and I hauling each other up some high bars left my legs shaking - and my pelvic floor did NOT appreciate the trampolines.
Raft building and racing was as crazy and wet as you'd expect.
Take lots of old clothes and some shoes you don't mind getting drenched/muddy. Also, leggings or joggers and long-sleeved tops (not cropped) that are comfy under a harness.
Loads of stuff in the evenings - bar, karaoke, discos etc. It all felt very safe, and the kids basically roamed free (with a few ground rules...) while the grown-ups recovered with a beer or two.
The accommodation was very basic (think youth hostel bunks) but clean and comfy. We were in the main hall, and my friend and her boys were in a little cabin-type room in the grounds.
I loved the food - very school canteen, but absolutely fine. The most amazing coffee that we downed by the gallon.
We had one "day off", so we took a boat trip to Dartmouth, which was a nice change of scene (and I think most of the kids were free).
Have an excellent (and exhausting!) time!