I've always played using the later option; ie, picking up Campbletown's crew just like picking up any other boat's crew. Incidentally, that's how it happened in the actual raid - Wynn maneuvered his MTB alongside the old destroyer and took on the remainder of her crew before withdrawaling.
Cheers! Great game, isn't it?!
Thank you. Yes, in the end I played it this way too. It is really a great game. I purchased it many many years ago and only played it once. I am now playing it and it is great fun!