PC trial definitely works on a full PC client, I've already tried that. PS4 I don't know about for trial as never tried that, but the full game (on his PSN) would definitely work just fine.

Definitely don't put him on your account, apart from breaking SE's rules (account sharing), you'd have massive problems later if they wanted to keep playing since would be unable to move character off to a different account and would have to start over.