RE: Young Instructors
I don't think that age is important, but the relationship between the student and the instructor is. We have a young instructor at our field (16 when he started instructing). He usually teaches the younger pilots to fly and the older instructor teach the older pilots. For the most part this works out good.
When I started looking for instructor for my full scale license I met with 4 or 5 before I decide on the one that I felt like I could communicate with the best.
Learning will be faster if you and the student both enjoy it. Teach the ones you are comfortable with and pass on the ones you are not, but always make time for yourself or you will burn out fast.