Ahoy, I'm going to throw a monkey wrench into the discussion. I live & keep my boat south of Portland but have spent plenty of time in Casco Bay. Casco Bay is definitely a nice area but busy & congested on summer weekends. When you want to cruise you will almost always head east and go around the corner towards Boothbay & beyond. I would like to suggest you add a little bit more of a drive and position your boat closer to real cruising grounds - Robinhood Marine http://www.robinhoodmarinecenter.com/
It's just off the west side of the Sheepscot River in Riggs Cove. It's a beautiful quiet spot, full service, moorings & slips, lots of parking, and includes a decent restaurant. You are then available to three big rivers, great day trips, easy overnight trips, and only 90 min to the next big bay, Muscongus Bay, and only 3 hours to Penobscot Bay. Plus you can always go right and pop down into Casco Bay for an overnight.
Find yourself a copy of the Maine Cruising Guide. This is the bible for cruising in ME. http://www.mainecoastguide.com/guides.html
Have fun and hope to see you around next season.