Do you print off their workouts for them?
We use excel for our lifting sheets so for me I would set it up on google docs. 98% of our kids could get to it off their phone and update it. The other 2% could do it through one of their friends phones. Allow them access to make changes. They could see their workout and then update it if they were able to get more weight than given. Also, ours is formula based so if they up their max it automatically ups their weight for different sets.