COE = (Army) Corps of Engineers
I've been to Apple Island Resort, and thought it fairly nice and generally along the lines of what you want. The sites are somewhat closer together than I would prefer, but otherwise it checks most of the important boxes you want: full hookups, plenty of grownup-oriented activities in the area, and the Lake Champlain islands in general are pleasant.
I do hear consistently very good reviews of Lake George RV Park (which is nearly in New England). It may be more of a family-oriented rather than adult-oriented place for you. I have not stayed there myself. The Lake George area does have a great many things to do, many touristy but others less so.