There are several good campgrounds around the Lake George area, with almost any level of amenities to like. We kind of like the Daggett Lake Campsites near Warrensburg but it is isolated and somewhat primitive, so not everybody's cup of tea.
NY State parks in the Adirondacks are mostly not designed to accomodate RVs of any size. However, the Sacandaga Lake park on the southeastern border of the Adirondack Park is one decent one. http://www.dec.state.ny.us/website/do/camping/campgrounds/sacandaga.html
Here's some info on the area:
Please be more specific about where and what types of things you wish to see & do.
The Adirondacks cover a large area. Near the center is Lake Placid which was a former Olympics location. The population of the towns tend to be a few of thousand people. The center is rather unpopulated and rustic compared to Lake George, Thousand Is., Lake Ontario Beaches, etc. The campgrounds tend to be small, nice, quite, and simple instead of the large RV Resort versions.