Gifts

I'm looking for some opinions. My husband's family likes to buy my son stuff all the time. Books, clothes, toys, etc. He gets gifts for Valentine's Day, St. Patrick's Day, Easter, Halloween, Thanksgiving, Christmas, etc. One of my husband's aunts has something for my son almost every time we see her and even gives stuff to my mother-in-law to give us in between time. I think it's too much and I'm afraid my son will get spoiled. Not to mention it's a lot of stuff to have in our house. We have more books than we know what to do with and plenty of toys. His family is incredibly generous and they mean well, but it drives me crazy. My mother-in-law asked me if there are any books or toys he needs because she wants to buy him something for Halloween. I never really celebrated Halloween as a kid, and it's not a holiday that I think warrants gifts. She mentioned getting him an upholstered chair from Pottery Barn Kids. They are adorable, but it's too much for a Halloween gift. I want to tell her that we would prefer to keep gifts to holidays where it's customary to give gifts, primarily Birthday and Christmas, maybe Valentine's Day. I don't want to be rude and I don't want to seem ungrateful, but it's something that's been bugging me. I just don't know how to bring it up. I really don't want to hurt her feelings. Am I wrong for feeling this way?