Since everyone involved knows each other if something comes up that you feel 2 of the parties need to discuss with each other why not suggest just that? It's more complicated if people don't know each other (or don't know each other well). I see your role as working with the person who is talking to you to come up with the best way to respectfully approach the other party.
Everything will be ok in the end. If it's not ok it's not the end.