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Huzzah, you is alive!
Signed up, and added you for the donator only draws.
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Signed up! Added your games to draw on the 25th.
Ohhh... I'll sign up for that Crusader Kings II, please!
Added!
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Added myself for:
Deus Ex: Human Revolution Director's Cut
Hostile Waters: Antaeus Rising
Spirits
Toki Tori 2+
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(get Dad into some video games stuff)
Added for the things for you.
I'll leave it to the individual donators whether they want to entertain your request... Darkmere has already spoken re: Portal 1 + 2.
I think your heart is in the right place, but I'm curious... have you gotten him to try any games on your account? Portal isn't a terrible place to start; even if he has to redo it on his own copy, the warm up levels won't take more than an hour or so. Has he ever had a thing for board games? There's digital versions of some, and many high-abstraction strategy games play a lot like a board game. Puzzle games (for which Splice could qualify) are playable by most folks with living brain cells to rub together; Popcap has a free basic browser version of several major titles on their website. Testing the waters would be wise before gifts get tied to accounts.
The whole idea will probably work better if it's less on the surprise and more on the collaboration. Some digging, discussion, and generating a wishlist will help, methinks... then he can get games he is interested in and his computer can also handle. Games you can play together are a good idea too; Minecraft has definitely improved my relationship with my daughter over the last year, even though she and I butt heads on labor priorities sometimes.
All that said, even if you are unable to get things for him here, the titles you listed can be had cheap on Steam's Xmas sale if you're diligent... less than 20 bucks for all of 'em. GOG may also have good classics on the cheap (even off-sale) in the event Dad's box isn't beefy enough for modern-ish titles. Good luck!