Christmas Presents

My MIL and SIL are notorious for buying big in both sizes of things and amount (if not big items will buy lots of things) for birthdays, Christmas or whenever SIL comes to visit (she lives abroad in their home country) and despite our requests to not MIL brings something almost every time she comes over. We currently live in a one bed granny annexe with limited space that we rent off of my husband's great aunt and uncle who spend half their time here and the other half in their home country. So for the time being we have been able to keep some bits in theirs but They come back this weekend so that option is no longer valid. But anyway, back to my initial point. My husband and I are currently in the process of purchasing our home and he requested to them that please can they only buy the girls something small and said that ice got an ideas list on Amazon if they were unsure and his SIL was like what if we don't want to get something from there, he sais that's fine but please, not too much and to give them money for either their savings or so we can get something for them when we are all settled in. Now, they were talking in their home language but I could understand the gist that SIL was not happy and didn't like what we suggested and husband said when I asked him later what she said. I said that they're more than welcome to get them something nice after we're all settled and have a second Christmas if they wanted to for a compromise. I'm absolutely dreading them going against our wishes and buying something too big or too much just to disrespect us when they know we have so much else going on already and so much stuff to sort through. If anyone has any advice on what we can say to them to try to make sure they understand our request and why we've asked it we would be very grateful.