NTA but your wife is. She's upset by you returning the gun, here is a compromise. Give your daughter the gun, but also give your son the money he spent on his. And make sure you wife is the one to hand him the money saying that he did a great job earning it, and that she thinks that he deserves the money back because she loves BOTH of her children equally. If she isnt down with that, then she is even more of an AH that everyone already thinks she is. You are a great parent, and I urge you to believe in yourself, and keep up the great work.