Obviously I don't know the dynamics of your relationship with your in-laws at all but working from what you've presented in this thread I honestly don't think this is about the presents at all.
I think it's a power struggle & you want to control what the gps give your children ; when.
In all honesty none of the presents that you've listed would give me stress or sleepless nights. It's a lot of books / video games, a couple of soft toys & consumables - felt tip pens & lip gloss & sweets. As a pp has said if your dc is interested in animals it is a thoughtful enough selection
Are you concerned that gps are giving more presents than you / Santa are?
There's something more going on here because gps taking an interest & putting thought & effort into getting presents for your dc shouldn't be a cause of such high levels of stress & anxiety & perhaps that needs looking at?
My parents always bought loads for my dc, my in-laws v v little through a mixture of different family culture around gifts/ Christmas (V little effort made at all) & just not bothering. For dcs sake I would have e loved the in-laws to make a tiny bit more effort but it was What it was.
Can't you do a clear out of the stuff your dc already have & donate anything still working in advance of them opening their presents?
We lived in a v small house when I was growing up & my favourite aunty excelled at getting us big impressive (not necessarily expensive!) Presents & the excitement of those big parcels under the tree was amazing. They were mostly things like a woven straw dolls moses basket bit you could almost fit a real baby into it. Another year I got a wooden high chair for my tiny tears doll etc. We loved that aunty she was kind & thoughtful & fun & her presents were the best & my mum (her sister) never made a fuss about these new toys. Everyone was excited to see what was in the big parcel & we always raced to open them 1st. My other aunt (mums other sister) always gave sensible but dull presents like pjs or dressing gowns which we tolerated but didn't excite us
Don't ruin it for your dc, they're only small for such a short time