Congrats! Don't worry, your partner will be there. However, to ease your mind... If your partner does not contact you at least 24 hours before the game, call him. That way you'll know for sure he's coming.
But just to be safe, carry two extra whistles. If your partner doesn't show, give each coach a whistle, and tell them they've been drafted to form a three man crew. If they complain, tell them that this will likely be the only game EVER where you will care about their opinion on any play.