My camping buds include 2 basset hounds. Ideally I use a long leash reaching from a tree opposite the Scamp
extending back and ending at my door. No tangles and easy for a quick tie out if needed during the night. I have a coupler that allows two dogs on one leash. A few feet apart but not enough to tangle. Picture a "y" shaped system. Dogs connect to the top of the "y", tail of the "y" tied to a tree. And since they're usually both vying for a spot next to me, leashed close to each other works :-)
For cooling down, I freeze those soft sided bottles and place them where they can lie next to or on them.