RyuGin
Do what you want. If the mc is excited to go with them, let him go. after all as income you can exit. Remember that this is a fanfic and not One piece. So for that reason, go crazy with the plot if you want. And remember that he can't bring people with him, for now, so look for reasonable methods to make this happen. The Kame House master's mafuza is a good method... and don't forget the fruit that turns people into toys in the Dessrosa arc (I think it's called that xd). I say this because from minute zero you wanted to make Nami queen. And I highly doubt you already have a method for bringing "beings" into the real world. Or yes, I don't know, I'm just saying.