It's up to the creator. Thank you for permission

The site rule says that the creator reserves the right to reroll anytime if the winner owns any base game in the package, even if the creator previously gave explicit wording that it is alright, such as you just did (a moderator confirmed this some time ago). In other words, you are not bound by your word if you change your mind.
A single key will work for anyone that does not own everything in the package already - even if they lack just one DLC, the entire key will be consumed and the leftovers are simply 'wasted'. If they own everything in the key, however, the key will remain unused.