In laws taking over

My partners grandma has very kindly bought the nursery furniture and pram for us. She let us choose the ones we wanted and everything was fine. Although now the mother in a law and grandmother have totally taken over everything. They keep buying everything and now they've even stopped asked our opinion and just buy it and show us after. Yesterday they bought a high chair without checking with us first. I've had my heart set on a certain one for a long time and my MIL knew this and still bought a totally different one which I don't really like. My MIL also tried to invite a load of HER friends (people I don't know) to my baby shower! This was an argument that was had last week and my partner was totally stuck in the middle and they're not thinking about their son or me. I feel like they have totally taken over and taken away the exciting parts for us. I don't want to seem ungrateful but they have upset me so many times already. My family is also upset as there is literally nothing else left for them to buy for the baby. My other half is annoyed with them but it's an awkward situation because they're not exactly being mean, it's just so frustrating because I feel like all of our choices have been taken away from us. I feel like they think this is THEIR baby. I don't know what to do. I don't do well with confrontation and I don't want to upset anyone or my partner but it's really stressing me out and it's making me worry about our little girl. I need to say something now before it gets worse, I just don't know what to say. I feel like they're being quite selfish and they keep posting things online bragging about all the things they have bought for our baby and it's obvious why they are doing it. I know they're excited but it's kind of taking the magic away from us :/ any advice will be greatly appreciated. Like I said I really appreciate everything they're doing I just wish they'd think a little first. Thank you x