An Adirondack shelter is an open fronted wood structure, usually with sleeping platforms arranged like bunk beds. You bring your sleeping gear (pad, bag or quilt). I've slept in quite a few, as I generally try to use them in off seasons. The ones on the trail you wish to hike on sound large and heavily used. I would not plan on finding a space in them, but bring a shelter to use in the tent pads. Even if you do get a space inside, I've often set our small tent up right on the sleeping platforms to provide bug protection and a little privacy. Many people do. Hard to do on the top bunk, easier on the bottom if you have a small free standing tent. The shelters provide a little wind protection, but offer nothing for warmth. Don't count on them doing anything other than helping to stay dry in the rain. I did a backpack outside of Johnstown long about 1975, as I had a friend living there and going to Carnegie-Mellon. I don't remember a great deal,(if you remember the 70's you weren't there... ) other than it was a very pretty area, and the hiking wasn't extreme. Sounds like a perfect choice for your trip. There's a lot to figure out for gear, do the research, ask the questions, and you'll have a lot of fun. You made a good choice to come here. I'm in awe of some of the members experience here. A WEALTH of knowledge.