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It is always good to have a counsel for anything like this. The mediator though is there to make sure the he is not bullied.
The mediator doesn't make rulings or even push for a resolution. The mediator is just there to keep things civil, help both parties to have their say and move on from there. So your concerns about him being bullied at this meeting aren't really something to worry about, because the entire purpose of a mediator is to make sure that doesn't happen.
Yes, that can be part of it, but it's not terribly common. You are correct in assuming that no substantial offer would be made. The purpose of a mediation is to find common ground and to see if a resolution can be reached without substantial expense. It's also a discovery process (so an opportunity for both side to learn something about the arguments of the other side in a low threat environment). They are worth doing, but do not commonly result in a resolution, just information.
Yes, I can accept a call, but that's a different process on here and I have to treat it as an additional service in order to send you a secured phone number to use. I certainly don't mind, but it is a different process than this.