If they are volunteering they probably don't expect to be paid for their efforts. I think you should wait until you can gauge each individuals level of contribution before offering any sats. It is hard to say how much without knowing the time commitment, difficulty of the work, aptitude and dedication of the parties involved. If it is not too much of a time commitment you may just want to give each 100k sats but if it is a big time commitment it is probably better to wait and decide individually how you would like to reward each one.