Just a suggestion, but maybe it could be an idea to spread the distribution a little. Now, if the post reaches a $5 payout, 1 winner gets all cards.

Why not set different limits, like giving away one card when the post payout reaches $1, 2 when the post payout reaches $2 and so one.

You could award multiple participants that way, making it more attractive for people to join.

But that's just my two cents :0)