I know I will probably come across as ungrateful, and honestly I should think I am a bit. Recently MIL has bought my 2 pre school age boys a lovely (expensive) pair of jeans each. I've managed to get the 3 yr old to wear them once (To visit mil) but I know he won't wear them again. The younger one spends the entire time pulling at his legs. She also bought them , again lovely, pjs each. Which would be great except I have already bought the exact same set for Christmas. Stbx came along with a thick fleece hoody for them, when they already have 2 each which are very warm and were gifts from other relatives which he knows about. Ds1 cried when he showed me his as he said "I didn't want it but Daddy chose it". So, he has 2 he will happily wear and this one he won't. I'm not going to argue with a 3 yr old when he's said from the start he doesn't want it.
I think it's lively that they like to buy things for the children but I do wish they'd buy stuff that they need, or at least that they like. It's very difficult to refuse as things are still awkward after splitting up.