We stayed in one of the yurts, and I was perfect for the group of 6 I went with. It dumped rain the first night we were there and the yurt kept us perfectly comfortable and dry. There is fishing, boating, hiking, and all sorts of activities to do around the park. We rented a pontoon boat for one afternoon and explored the lake, which was awesome. I will say the "beach area" we visited was less than clean and quite small. However, the trip was a blast overall and if you're looking for a quick weekend trip, this is a place to go.
The private island is a beautiful campsite and has enough room for several tents. There's plenty of trees on the island so there are plenty of sticks to find for fires, and even if you want logs you can buy some at the office and they'll dump a truckload of wood that can last you the whole weekend. The creek surrounding the island does make it cold at night so make sure to pack warmly.