I am in the Boston area too and wish I could convince my wife to live aboard. I have talked to many people who are doing this and Constitution Marina in East Boston seems to be the best place for winter live a boards. Some people I have talked to, spend the winters there and move down to places like Hingham for the summer.
My biggest suggestion is to try living a board with the kids before you commit. At Constitution Marina they have a bed and breakfast were you stay on a boat. Bed and Breakfast, on a boat!
They have a number of sailboats you could try.
As far as the boat, I would not be so quick to rule out Catalinas. While they are not typically the potential blue water boat that you may want, you can get a lot more boat for the money and they usually have great resale value. You could learn to sail on the Catalina, make your mistakes, then sell the boat and move up to the blue water boat.
Of the boats you listed, my preference would be the C&C landfall. We had a C&C before our current Catalina. They seem to be well built and have reasonably good access for maintaining most systems.
Also, when it is time to buy, I highly recommend Peter Hunt as a surveyor. We used him on our Catalina 310. He was great. Took the entire day and wouldn't leave until we were comfortable with the various system and explained everything from basic diesel maintenance (had a small out board on our last boat) to making sure we knew how to operate the radar.
Which ever way you go, good luck. Hope to see you on the water this spring.