Group Mentoring Training Curriculum

We received a short term grant (1 year with the possibility or 4 more years) and we will be offering group mentoring in conjunction with an abstinence-based health curriculum for 7th graders. Without getting into all the details, it is a demonstration grant and they are hoping to tie together this curriculum/mentoring with a reduced rate of teen pregnancy. Anyway, I am looking for some materials/resources to help us prepare our mentors for (gasp!) a group of 5 7th graders. The mentors will be doing set activities with the students (activities pulled from a workbook published by Search Institute - they will actually be doing asset-building activities!) so they will have material and something to work from but I just want them to be a little more prepared in the group-facilitation area. We have come up kinda short with internet searches. Any ideas? Does any mentoring program out there focus any part of their mentor training on group mentoring? Any help or referral you could offer would be great!