Your post on cruising with another family was the one to finally get me to register here. We have been looking at the same thing so I'd be interested to learn what you've discovered. I see the general feelings at this point in your thread are fairly negative towards the idea, but to me any situation is a compromise for a goal and its all what you make of it. Sure, there's always potential for it to be a terrible idea, but in the same way, it could also be amazing! Plus, if it gets you where you think you want to be!
One night over a few drinks I tossed the idea of going together with another family and so far its seems they jumped on it. At the time I was thinking it might stretch a dollar a bit further and get us both we we think we want to be.
That wasn't the only factor for me/us though. I wrote a longer discussion but this didn't allow for my excessive wordiness (limit of 1000 char's), so if you're interested in more, maybe send an email or whatever.