Where will the wedding be held? Perhaps you may want to headquarter out of the same place all week? Will you have a car?
When we travel to MA, we split our time south of Boston near the water and a few days in the city. We like the Home Suites Inn in Waltham on Totten Road. It is just a short drive to a T-stop go into the city for the day and not too far to the water.
We have gone on the Old Town Trolley Tour and loved it...
www.trolleytours.com You can hop off and on the trolley all day at any of the stops. You can buy a one day or two day pass .... I just checked the website and see that the 2nd day is free! That is a great deal and I wish we would have had that last year!
The bus drivers/tour directors are very knowledgeable and often quite funny. It was definitely worth the price - which seems high to begin with, but truly 'made' our trip. On this tour we also went on the Swan Boats, the North End (Mike's Pastries included), the USS Constitution, Old North Church, Freedom Trail, Paul Revere's house, Fanueil Hall, Quincy Market, Boston Garden, saw the Cheers bar, cemetary of Mother Goose and Benjamin Franklin, saw the Christopher Columbus statue in the North End, and much more. Much is outlined on the website, but the bus drivers ad lib a lot and tell you more too.
Other things we've done and enjoyed - Museum of Science (hint: buy a membership at your local zoo and enjoy FREE or reduced admission to MoS with their reciprocity deals). We got in for free. It would have been $84 for our family of 4 - and our local zoo membership was only $53. We only had 1 day at MoS, but could have easily spent 2 days there.
There are also a few zoos in the Boston area and one in Providence that offer free or reduced admission with your local zoo pass. We flew in and out of Providence (cheaper than Logan/Boston), so we went to the zoo down there as well. The website for our local zoo has a listing of what zoos/museums participate and perhaps if you have a local/regional zoo, it may as well.
If you are a baseball fan, especially a RED SOX fan, you can't miss Fenway Park. We went to a game one night and then came back the next day to tour the stadium. Very interesting! Game tickets are pricey, but we found some for a decent price on ebay.
If you are football fan, especially a PATRIOTS fan, and you are there at the right time, you might be able to go to their Training Camp in Foxboro. It is free and open to the public.
Shopping ... be sure to find a few Christmas Tree Shops .... or 5 or 6 ....

. There are several south of the city and down through Cape Cod and though they all have some of the same products, they seem to each have some different items too. And GREAT prices. Fun stores. Likely in other areas north and west too.
Filene's Basement ... if you take the trolley tour, you will go past the main store in the city. It is really fun to shop there, but there are other Filene's stores too. One of those " Boston institution" type of stores. We don't go every tim, but you should go at least once.
In the south, both Scituate and Plymouth have great areas to walk around with restaurants and shops of all kinds - antique, gift shops, pretty much anything. Scituate has the lighthouse and Plymouth, of course, has Plymouth Rock and the Mayflower 2 ship. Marshfield (between Scituate and Plymouth) has a great public beach, as do some towns down along the Cape. If you want to have the pilgrim experience, be sure to go to Plimouth Plantation in Plymouth.
There is SO much to do both in the city and away from the city. Since we split our time in both areas, having a hotel that has decent access to both works well for us.
Whatever you decide, I am sure you have a fabulous time!!!
