I haven't stayed on the Queen Mary but I've done the tour. I thought it was well worth the money (although, funnily enough, nobody checked our tickets so in theory we could have taken the tour for free!). I keep wanting to do the tour again but my girlfriend wasn't as enthralled as I was, although she did like it. I also recommend taking the ghost tour, or whatever they call it. It's well worth seeing the old engine room and bow of the ship from the inside. I think the ghost tour is included in one of the ticket prices but I don't remember for sure. I know you can visit the old Russian submarine for a little extra, which I haven't done (I seem to remember it being $20 extra or something and I felt that was way too steep).

My boss has a boat he keeps moored in Long Beach and I've been out in the water on the other side of the Queen Mary too. It's always beautiful from any angle but especially from the sea. I hope you have a great time!