Give away 14 leftover (humble)bundle keys

Wow pretty good list there. You could always give to unlucky 7. Probably get some played from there.

Playing Appreciated would be the best bet!

Playing Appreciated is closed to join right now but there's 2 other groups I know of with low requirements, if you can get to level 2 :)
Taleplay Games won need to be played in 3 months
Knights of Havenshire You can require that the winner play your game *The group has a 1 giveaway needs to be created each month rule though... maybe not ideal for you?

You could create a whitelist of people who genuinely play/enjoy what they win or seem trustworthy and kind enough that if you ask in the description for it to be played, they will :)

Also unfortunately you can't give gog or rockstar keys on here, only steam keys!

I wanna enter for that wargroove key. It might take me a while to play since I just had a kid but I'll get to it eventually

You could put them up for Play a Game You Won on SteamGifts, perhaps? There's a group for them that's restricted to people who play, but you could make them invite-only and provide the links to samwise84 (think that's right) and they'd be part of the monthly giveaways for people who have played a game and qualify. Since there's impetus to play the games every month, they have a good chance of getting played once won.
https://www.steamgifts.com/discussion/X1Ks6/october-is-a-play-a-game-you-won-on-steamgifts-month-riddle-me-this

Otherwise, Taleplay seems like a good fit, linked above a few posts.