Two Penny, at the expense of seeming unsupportive of you.... my very opinionated opinion is to take the gifts. People often want to make the other person happy by giving it. It's flattering.
Your son isn't going to care who provided the gift. The Christmas tree picking out is so much fun on it's own. And the decorating of it etc.
For kids sometimes the wanting of something can be more passionate then the receiving of it too.
Anywho, my two cents is that it's okay to give away food you can't use. Or toss it out if you don't like it.
For your son I'm sure with a handful of presents and the tree etc. It will be fun. It's especially fun when one gets to camp out in living room and sleep under the Christmas tree !
Sleeping under the Christmas tree is like my favorite memory mainly because I didn't have to sleep in my bed....it was subversive LOL
Try to chill-lax a little about Christmas. It's more the experience than the gift itself which is important. Do something fun!!!!!!
Go out look at Christmas displays! Get a ginger bread kit! You can just use graham crackers too and make little houses.
Make hot cider or hot chocolate and watch movies at home etc. It will be good whatever happens.
You can also tell the person who is sending the late present that somebody else got the same exact present!!! And you had no idea that was going to happen and your son already used it so you can't return in therefore.... you may have to return the duplicate gift for something else etc. Maybe you can just exchange it, maybe they will send a receipt.
At work I have to set up large quotes for people sometimes I have a hard time asking people for the full price though I think I am getting better.
Money and things are hard to waste if you have ever gone without. It's just not worth it to say stuff to people because it hurts their feelings etc, it can take the joy out of giving. Better to just tell them how overwhelmingly excited your son was and he even wanted to keep the duplicate one or something like that. I don't know what the present is exactly.
Kids also feel important when people outside of their immediate family recognize them. (In my opinion again

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Okay that is my response.