We stayed for 2 nights, which was just about right. 1 night, and it seems like you come and go too quickly to enjoy anything. 3 nights is likely too long to keep everyone occupied. We did the zip-line, which was about 7-9 lines through the trees and across the meadow. Our 7 year old had no problems, and the guides were great. We also did a horseback ride and a tie-dye project, and both were a lot of fun.
It was not difficult getting in and out of the treehouse. Using the pulley was a great learning experience for the kids. And meeting our "neighbors" during the vacation was easy and a lot of fun. Folks congregate around the firepit at night, and also during lunch and dinner. Be sure to pack what food you need, since the town is 12 miles away. They do serve breakfast, and it was great. Much better than anything at a chain hotel.
The one downside really didn't apply to us, but I noticed that teenage kids were a bit bored. The zip lines were popular, but aside from that, they just walked around a lot. This really does seem geared towards young families.