As you make him and only him wear fancy dress for the duration. Oh his face, he didn't expect this, cameras ready and we'll have a copy too please.
Take your pick from a multitude of ideas, but some of our favourites have to include:
Anything really that involves lots of lycra is a winner.
Go for the hassle-free option, don't waste hours planning, only to end up with a full-time job sorting out payments from guys you might not know to suppliers you have never used before. That's our job, you simply pick the best activities / accommodation and leave us to get it sorted. Then sit back and take all the credit.