That sounds like a great idea!
I would probaly call them loungewear pants instead of PJ bottoms because the new sewists will want to show them around and you usualy don't show around your sleepwear ;-)
First off - congratulations on your bravery to open this venture.
Second - query, are you sure that a pleated skirt is suitable for beginners? unless it is a pleat a tube onto a waistband variety, I would have thought that an A-line might be better.
I think it sounds like an awesome idea. My aunt and I had tossed around a similar idea but I don't have the space since I still live at home.
Make sure they sign some sort of a waiver, in case they injure themselves while sewing. Otherwise anything that happens to them, they could sue you for, even something dumb like tripping over a cord.
Thanks Lisette I had already thought of that too!