Probably shouldn't let him become too unappreciative. Not telling you how to raise your own kids of course, but man, I remember my sister returning her Bday gift from my mom and using the money to buy her friend a gift. When I heard about that shyt, it really made me feel a way, because she was always appreciative when she was younger just like the rest of my siblings. Moms also always flat out looked at her kids and if she noticed something was off she would just say exchange it for the one that you want. So if you see the Xbox just laying there, just ask him if he wants to go to the store and trade it for a Wii U.
Or by Wii U did he mean the Switch? lol