First things first, may you have a better lap around the local star on this ball of rock and metal that we keep trashing as if we and all the other species we share (or should be sharing) it with had piles more to spare.
As for your very generous giveaway... Been very lucky with a couple of other big ones this year, one of them recently, so meant not to enter... until I saw the requirement and... No SO, but Thursday just marked one more year since she left me... And... yeah...
So, first thing I did, and would do, assuming she'd still want that, would be to leave her alone. If at all possible on her birthday when we were together she'd stay awake till morning, turn off her phone and sleep as much of the day away as she could, wanting to avoid all the typical calls and cliche messages. So mainly be quiet and give her space, but other than that whatever home-y stuff she'd want. Maybe (try to) cook something, likely simple but potentially very time consuming if she'd want that, watch whatever she'd want to watch together, tempted to also say cuddle a lot but I was more with the cuddling that she was so probably won't count, and if she'd want to go past cuddling then pay particular attention to, well, won't go into further details if you don't mind.
There's this tendency, doing things supposedly for your SO, and actually believing that you do it for them, but in fact doing it more for yourself, doing things you want to do, even if it's a matter of wanting to do them together or wanting to do it for them. But if you want to do something actually for them, that may only be exactly what they want you to do. If it seems too much or something you don't want to do, there is a lack of compatibility in certain areas that needs addressing, but if it makes you feel that you're not doing enough, or that it's not something that'd "count", well, putting that aside and settling for the fact that it is enough and counts for them may well be your actual gift to them.
That said... I'm in for:
1. Dragon Age™: Origins - Ultimate Edition
2. Sea Dogs: City of Abandoned Ships
3. Sea Dogs: Caribbean Tales