Great idea! Allow me to suggest a few things.
Post on the chosen MB asking for a tour guide. I know someone already volunteered, but this will start getting the other MB used to the idea of a SAMB vacation. We can have more than one, but we need to have at least one.
While you're at it, it would probably be a good idea to have a poll and ask the other MB if it's okay if we do a visit.
Before anyone makes a thread on the other MB regarding this event, post it here first so we can make sure your draft won't ruffle any feathers, even unintentionally.
Ask the tour guides to find posts for us to visit. This involves asking MBers if we can come post on their threads. Be sure to tell them that you have no way of knowing how many will participate.
Also ask the tour guides to ask others to set up places for us to visit, like a hotel, restaurants, a gift shop/shopping center, various entertainment venues, local celebrity homes/landmarks, a beach/hiking trails, etc. Again, don't overdo it.
Have a code of conduct. Visitors must be respectful of the MB's wishes (someone might have already said this), must not flood the MB with vacation topics, possibly edit their sigs to show they are visitors, etc.
There should also be a main thead on the other MB called "The Tour Bus" or something similarish. This would be the home thread of the vacation and where the tour guides post the link to the next topic. I recommend tour guides edit their sig to show they are tour guides so they're easy to find.
Limit the vacation time (credit). The tour guide is in charge of this of course, as they'll know how thick or thin the MB's patience is, but I would recommend a few days, and no more than a week.
I'll post if I come up with anything else.