well I just played several rounds to give the game a trial.
suggestions:
your site needs a FAQ for the players.
each game should show its end time or do you just play until all tickets are sold ?
As for random number issues, (Im still a bit groggy from my recovery) but I dont see any exposed secrets ?
That aside - on small rounds like this for me at least its not a large concern.
my suggestion for picking a winner.
sha512 (public secret * player 1 nick * player 2 nick * player 3 nick * etc ) then pick a slice that determines your random number.^ Im not a crypotologist though, someone else here can weigh in on this.
edit: Im an idiot, the last player to play could determine which number wins. (still groggy ok

)
another option is just like bitlotto
lotto numbers (we have weekly ones here, it would be a non issue to find a regular public pseudo random source).
sha512(public secret * lotto numbers);
anyway good luck

I made several bets to get the games rolling for you.