I'm fine with this, but just so you don't get into trouble with the moderators, just have the winner agree to delete the GA after it ends if the key doesn't work. Usually, people are willing to do so. After that, you can either create a different GA for this other game or give it to the winner if they agree to delete the GA just because you want to.

Basically, I said all that just to help you from possibly getting a strike of some kind here.

Cheers & Have a Great Day!
c[O,..,O]p

Thank you~