Lake George RV Park is our favorite. Been going there for years, including when my kids were around the same age as yours. They offer a lot of activities for all ages. The Lake George area has lots of other things to do as well. Lake George Village itself offers a variety of different activities.
http://www.lakegeorge.com/news/itinerary-kids.cfm (It is not Ocean City, but I think you will find plenty to stay busy). Also, just down the road is Six Flags, Great Escape, if all else fails.
http://www.sixflags.com/greatEscape/index.aspx