If you are staying near the Pru then I have a few additional recommendations. Take a walk down Boylston Street to the Common and the Public Garden. Take a ride on the Swan Boats and then head over to Fire and Ice on nearby Berkeley Street to eat. You gather all your ingredients (meat, fish, pasta, vegetables, etc.) in a bowl, choose a sauce (watch for the "fire ratings" to see how hot it is), and then take it to a giant grill in the center where they cook it for you. It's kind of like a grilled stir fry and the food is delicious. My kids love it - we were just there again on Sunday - and I'd recommend it highly. It can get crowded so going a little early or late is advisable.
If you are staying more than one day there is also a really fun comedy, murder mystery called Shear Madness that plays in the tiny basement theater of the Charles Playhouse (near the Common in the Theatre District). It's been there for more than 30 years and is a bit of a Boston institution. I won't give away the secrets, but suffice it to say there is some audience interaction and every family member we've taken has loved it. It includes everything from political comedy to slapstick so there is something for all ages. AAA members get a 25% discount. The Blue Man Group also plays in the theater upstairs so that is another option.
Lastly, since you'll be in the Prudential Center area, if you want kind of a casual dining place that is OK for all ages, there's a restaurant across the street from the Sheraton and Hines Convention Center on Dalton Street called Summer Shack (there are a few of them including at one of the casinos here in CT). In a city of fine seafood restaurants there are certainly better and more upscale options, but if you want a place that is convenient to your hotel, not too expensive and comfortable it is a good choice. Last year we parked at the Pru for a game, walked across the street to eat at this restaurant and then walked off our meal for 10-15 minutes on the way to Fenway.
