Play money sucks. Why not give out real money? That way people can truly test your site! Usually play money is easy to double in most casinos(hmm... I wonder why...). While real money is so hard to even get a 10% profit over it. I would love to try it out if there would be free money to play with and not just play money.
Except that this is a sportsbook. They have no control over the outcome of sports, unless they've fixed the matches, in which case it doesn't matter whether it's playmoney or dreams - you still win or lose based on actual games.