I think 3 trainees is the most I would do from an early age, I tend to do a lot of one position training ie OD so my young guys can stay on the floor long enough to get the whole 48 mins needed and only need one game each time to do it.
IMO both of the guys you have here are very far behind for 1 week to go being 18 yo's, you might be able to train them for a whole season and off load them for a little cash though if that is of interest to you. I would normally not pick up anything less than Superstar unless they were reasonably developed and even then they would be my 3rd guy in any case.
I just feel that if I am going to pay an expensive trainer and invest season long training into guys, then I want it to be worth it long term.