Not meaningless to op and her DH though?
Is this supposed to be an issue of an unfairly treated baby, or an adult, then?
Is perhaps the problem the meaning the OP attaches to random toys, then? Isn't it possible that the ten-month old is getting exactly the same amount of small gifts as the four-year-old got when he was ten months, or would've done, if he was part of the family?
You can buy stuff for 10p at charity shops and the like or supermarkets,.....a rattle? A little teddy? Much of which isn't suitable for a ten-month old who sticks everything in his mouth. You are still buying stuff for the sake of it. Presents are not the only way to show love, and random presents aren't a good way to show love to a baby. We hug and cuddle babies. We hug, cuddle and buy four-year-olds tiny plastic cars.
They want the OP to bring over food. Given we don't know what baby eats, that may be fair enough.
The holiday was cancelled, yes.
If the family is 'imploding', maybe it's because OP isn't happy and her DH isn't happy.
Nope, I'm not a grandparent. I do have young children though, and I remember how fast their tastes changed as babies and being a bit PFB about what they ate. I also notice that MIL is a lot more confident about looking after them on her own now they're not babies, and doesn't ask me to bring stuff over.
And it's NOT because she loves them more now!