My family owns a timeshare at the Marriott Custom House, across the street from the Longwarf. I just came back from a weeks trip (and I live 20 minutes away!!)
Must dos on our weeks in Boston are....
Neighborhood: North End
3 Mechanic St
(between Hanover Pl & Sumner Tunl)
Boston, MA 02113
(617) 523-0015
A 3 - 5 minute walk fro the Marriotts. This is a tiny tiny place nobody really knows about. It is in an alley and looks like a town house. You eat what used to be the living room. There are only 5 tables in there so reservations are a must. They are only open 3 days per week Thu/Fri/Sat for 3 hours each night 5 - 8. This is not a tourist trap!! True authentic Italian. They only accept cash, but the prices are super reasonable for HUGE portions and being in Boston! (Approx 15 - 20 per entree, 6 per appetizer). Dont forget Mikes Pastrys for a Cannoli on Hanover street for dessert!!! (Idas doesnt serve dessert)
Second is....
http://www.mysterycafe.com/
Another less than 5 minute walk from the hotel, at the Club Quarter's Elephant and Castle restaurant. This is a fun murder mystery show. Every couple of months they change the show. Now playing is a spoof of the Red Sox where someone kills pitcher Roger Lemons (last time is was American Homicidal, a spoof of American Idol where someone killed of the person who was about to win). Audience participation is as much as you want it to be. Fully involved or just watching! Food is good and for the price per person, you cant do much better for that in a regular Boston restaurant and be entertained!
We used to do the Fenway tours, but it is old school to us now. If you plan on doing trolleys, you should order
http://www.smartdestinations.com/attractionList.ep?filters=_d_Bos_Vip&pass=go
for $54 for one day or $79 for two days, you can ride all the trolleys, harbor cruises, duck tours you want. It also includes many of the museums for free admission and gives discounts at many restaurants. We use this card every time we go.
Last...I highly suggest Durgin Park in Fanuiel Hall. Its a tourist trap, but a great BOSTON restaurant. Prices are great, with great Bostonian food...Yankee Pot Roast, Seafood Platter, Baked Beans etc... (Bread pudding for dessert is to die for).
Oh..one more thing. If you have kids under 12, take them on the carousel across from the hotel before eating at Oceanas (restaurant inside Mariott Longwarf). The $3 carousel ride will get you a coupon for kids eat free at Oceanas.
ENJOY!