Replying to Mentally Challenged Skiers

My dads friend at works son helps mentally challenged kids with skiing, and my dad asked me if I wanted to do it, and of course I said yes (I'm an intermediate-advanced skier, been doing it since I was 2-3, We live in PA so the mountain is relatively small ect, ect). But what I would like to know is what exactly will I be doing to help them? Will I be helping with the actual skiing, just getting on the lift, teaching them how to ski, trying to advance them in their skiing level... or all of that? Theres going to be adults there too, and also I get some skiing time to myself after I'm done helping. Has anyone ever done something similar before? My dad only got limited information, and I start next thursday, and I'm sure they'll explain everything there, but I'm just asking if theres anything I need to know before going?