Planning a trip to Door County this summer. I know there's lots to do in terms of shopping and eating and just poking around. Also interested in Penninsula State Park, the ferry to Washington Island and Rock Island, and probably more. I'm just not sure how much time these things all take up and whether 3 days would be plenty of time or if 4 days would really be better. We'll have about a 3 1/2-4 hour drive to get there. Any advice as to how much time to allow and also any favorite places to see/do?