We've stayed at the Queen Mary many times and really enjoyed it (but it's been a number of years since we've been there). Touring the boat is a lot of fun and we all loved the history associated with the ship.
There are lots of places close by - but I don't know if they would be in walking distance, though - to go and do things (restaurants, movies, etc.).
I heard that they were again talking about closing the Queen Mary down which is a real shame because it's a beautiful ship.
We've been meaning to go down and spend a weekend there again!
You're going to have a blast. I've stayed on the boat and it's great. You can explore more than the walk on guests which is also fantastic. Take the tours. They're a little campy but you get to go into the bowels of the ship.