Bike ride near Boston

i am participating in the MS Cape Cod Get Away bike ride in late June and need to spend time on the bike seat to get ready. I'll be riding from Bajko Ice Rink in Hyde Park out to and in the Dover/Needham areas on some nice country roads where there are always lots of riders. I'll do about 12/13 mph. If so inclined, I'll stop to grab a sandwich while in Dover. You will need a helmet, have a spare tube and be able to ride at 12/13 mph for 3 to 4 hours. If Bajko Ice Rink is a safe place to park. It's at 79 Turtle Pond Parkway, Hyde Park MA 02136. I'll leave there by 11 am. If you plan to join me, email so I can decide to go  earlier if no one is coming.