We stayed in the suburbs and drove to the Bunker Hill end of the Freedom trail (easy parking) and walked unguided, my wife and I and 3 college age kids. Don't miss climbing the Bunker Hill Monument, but do it first before you are tired. Then its mostly downhill through to all the historical locations. Be aware some cost extra. Also, you'll need a photo ID at "Old Ironsides". Take plenty of water if its hot, the 2.5 miles could take many hours if you take time at all the sights.
A ride back to our car would have been a good idea!