MasterPetey: I have bought 6 games off G2A, and they all worked, uplay, steam and origin. take it or leave it, im sure itll work.
This is what everyone says when it's pointed out what a shady grey-market key-reseller G2A is. Sure, you bought some keys that worked. And that's great: you didn't get burned. Yet. But sooner or later it will happen. There are no providers of legitimate GOG keys other than GOG, some Kickstarter projects, and very very rarely there may be a GOG key provided in bundles like Humble (I actually only recall this happening once).
GOG has removed games from peoples' game shelves here before when it was discovered that the keys from G2A were obtained fraudulently, so beware of them.
That being said, +1 as well for the generous thought.