How many are going to need a bathroom at once though? I'm conceding a primary "public" bathroom that would be readily available from any location in the house, so having one more in a typically unused guest bedroom seems like it ought to be adequate; if there's a rush you DO have the option of opening up the other facilities to guests. It does seem premised on the idea that there will often be a lot more people present than actually live there though, and maybe that's why I'm balking; I'm not a terribly social person (which is part of why I didn't visit a sweet lady on her birthday. )