Are there kids in your group or just adults? If there are kids, be sure to check out the Radio Disney room at the Hines Convention Center. They always have bands playing, and they have games and activities for the kids. It's a lot of fun.
Make sure you get the program schedule in advance so that you can decide exactly what you'd like to do. There is a wide variety of events planned all over the city, and you should definitely try to have a plan in advance so that you can see everything you want to see.
Make sure you set aside some time to see the ice sculptures. They are always phenominal.
Dress in layers, and make sure you dress warm enough. It can get cold and windy when you are waiting for the fireworks and the parade to start.
I wouldn't worry about making reservations for a restaurant unless you want to go someplace very nice. There are tons of casual restaurants, and it's easy to just pop into one along Boylston Street or in the transportation building.
Have a great time!
Karen