Your Jounin will probably be fine.

I think we should play out the introduction of the group, and then we can just have the Zabuza mission be the first mission we do. It makes sense that the Hidden mist ninja are after Zabuza, a hidden mist criminal. Perhaps we already know about Zabuza's intent to attack the bridge, as opposed to just 'happening' upon him.

Maybe only the Jounin knows...Who knows.