I think your plans are good given your guests' interests. Duck Tours area great way to get some history and see a lot of the sites quickly, too. Have you been to the Beer Hall at the Harpoon Brewery? It's awesome, and great for visitors. We love Legal Harborside nearby the brewery too, but I wouldn't consider it cheap. No Name, Yankee Lobster, Barking Crab and James Hook are all right around there, too.
Also, they can definitely watch the fireworks up close on Friday. We always just stroll right up a few minutes before the show starts. It's easy to watch from the ends of a lot of the Back Bay streets. Another popular place to watch it is Telegraph Hill in Southie, but keep an eye out on the weather. We went a couple years ago and nearly got struck by lightning (a couple people very near us actually were struck).