Just let him in the Cafe Challenge league, and put up a side bet. You said there was room in there anyway.
You both send the money to Madison, and he holds it for the winner at the end of the year. I can't see how anyone would have a problem with Madison holding the cash. And if Madison is not interested, then I'm sure you could get another regular from here to hold the dough. Trevisc seems pretty honest to me. I'm not crazy about his advice, but he seems honest.
Eternal vigilance is the price of integrity.