Desert Sun provides no freebies as far as I know, am sure that you can have meals delivered there as well.
Terra Cotta does provide a nice continental breakfast and the afternoon snacks come with wine!

Am not sure about the number of guests at either place in the summer but weekends will be livelier for sure. Terra Cotta seemed to be full on the weekend that we were there, maybe half full during the week (but we had 5 of their 20 rooms!) Have read that DS is pretty empty during the week but it's a much bigger place, there probably are always a few couples there. Again, weekends are hopping.

Glen Eden will have residents around all the time, quite a few couples visiting on the weekend, I would guess. Can't speak about summer though, they had a decent crowd the weekend in October that we were there. They have a snack bar for sandwiches and such. Feel free to PM me with any more questions.