I would highly recommend getting Changing Course, by Debra Cantrell. Read it and then give it to your wife. It is an excellent resource for anyone trying to convince their spouse of the wisdom of the idea.
While Hinckley's are generally beautiful boats, you may want to consider a slightly smaller boat, especially if you'll be cruising in it at all. A 49' boat is rather difficult to single hand, and given that you have a young child, you would be effectively singlehanding the boat most of the time. I would recommend that you get something more in the range of 37-40' LOA, rather than something bigger. Anything smaller will probably be a bit cramped.
It would also help if you said what area you're planning on living aboard and sailing in. If you're not looking to sail the boat, why are you planning on living aboard???
It might be worth thinking about the long term costs as well. A 49' boat is going to take some serious bucks to maintain, dock, haul, etc. Most places charge by the foot for dock fees, haulout fees, cleaning and painting fees, so a 49' boat is going to be a lot more expensive than a 38' boat.
Also, the number of places you can go in a 38' boat may be off limits to a 49' boat. For instance, Rockport Harbor up on Cape Ann in Massachusetts, is fine for a 38' boat, but I'd hesitate to try getting a 49' boat in or out of there.