We stayed at the Marriott Copley that is about 1 block away from the finish line. It was nice to be right in the middle of things. Also, there was a grocery store across the street from the hotel which was convenient. We booked through marathontours.com and got a decent price on the room. I think that most of the rooms allocated to marathontours.com are filled but it is worth checking out. If you do decide to go, you will need to book a room soon because the women's Olympic trials are the Sunday before the marathon so it may be extra crowded.
Of course, a Red Sox game is a must. The game that we bought tickets for was rained out and that is probably the one thing that I missed the most. If you are able to walk the
Freedom trail, you will be able to hit all the major tourist attractions. I'm not sure how much walking Cody will want to do before the marathon, though. We went on the
Boston Duck Tours which I wasn't all that impressed with. We missed out on a lot of the stuff that we really wanted to do because of the bad weather this year.
As far as eating, I would recommend Legal Seafood and the Union Oyster House.
It is definitely a great trip and a well deserved reward for Cody's hard work and you putting up with a marathoner's lifestyle.