I think your best bets will be either the Poconos or Lehigh Valley regions, both of which cater to large groups and are close to outdoor recreation including hiking, fishing, biking, skiing, whitewater rafting, and canoeing. Visit http://away.com/active-adventure-vacations/index.html to explore outdoor-focused destinations in PA, including recommendations for places stay , things to do, and vacation rentals (possibly useful for your large group).