Do my apprentices need the app on their own phone?
No. They can work on a shared tablet with their own PIN, with no email address or login.
No. Set up a shared tablet for the van or the workshop and each of the crew taps their name and puts in their own PIN, so everything they do is recorded as theirs. Someone who only works on the tablet doesn't need an email address or a login. Shared tablets come with every plan.