Glad for you to do a giveaway like this, but doing Code dumps?... there are bots all over the internet that just search for these Steam Keys and use them for their "Bot" accounts.

They don't seem to have reached steemit yet, but they will....

The better way is to ask the winner for their steam ID, friend them on steam and give it to them via private message. I know it's hard to do for you but it insures that the one who got it is a member of this community and not a Bot.