Edit: nvm, only just saw this was a hilarious necro
The way these things usually work is that you provide proof of purchase and eventually get given a key for the game that you can use to add the game to a Steam account.
Therefore unless you want to share your personal data with randoms on the internet, you may need to go through the redemption process far enough to get the codes, then give the codes to people here.
If the giveway relies on account linking where you link an AMDRwards and (e.g.) Uplay account and the product is automatically added to the account without a key being used, then you may not be able to give them away. Although I think Uplay might be the only one of the main DRM clients to do that, and it's a relatively recent introduction, so it'll probably be keys.