Another possibility could be to assign new players who want help into groups such as children, teenagers and adults. Then pair each group with mentors respective to each category. This allows for players to feel more comfortable communicating to someone their age and perhaps form bonds to make friends. Of course, this proably has some flaws, but I'm not sure of the flaws at the moment.
I really like this idea. As an adult, I would not be interested in mentoring children nor would I want one to "mentor" me. I think there definitely should be a "quiz" of sorts for both mentors/mentees to take so they get matched with their best fit. One of the questions should be this and also timezones. I also think there should be an exit program with no hard feelings if the mentee/mentor don't work out.
I disagree with the idea that you can only have one mentee, as I have lots of free time and would be able to deal with multiple. Each mentor should have their own "student" before people start getting multiple though.
I also believe there should be a minimum limit of active time playing, depending on how many people sign up as mentors for this program. If only 3 people want to be mentors, then obviously the minimum could be much lower. But if it's a hit, then the minimum should be higher. 3 months playtime while being active nearly every day seems like a fair amount to me.
