As a conservative in a very liberal industry, I say "so?" I have no problem with discussing conflicting views and would feel insulted that someone would try to insulate me from the team's personality.
If your motivation is to help teammates avoid embarrassing themselves then simply mention that you've met these people before and they seem to be more conservative. If your teammates aren't afraid they will embarrass themselves then why should you worry for them?
I'm sure the people coming in to town haven't become senior members by having this skin. Let them speak for themselves if they don't appreciate the tone of conversation.