Congratulations on your new grandchild/step-grandchild (not sure what you have decided to refer to him as)
I must admit it is totally different for my parents when it comes to my partners son.
My parents have met my partners child (approximately 3 times in nearly 3 years), but due to the biomum being ... bizarre/unpredicable/unreasonable/strange/psychotic/angry/half-normal (at times) ... delete where applicable, this behaviour doesn't help anybody and I have no desire for my parents to be involved in any of her mad behaviour, so my parents aren't really involved in SS life (which I'm sure biomum is very happy about ... she'd be happier if I wasn't around either ... it seems she just wants my partner to become a sad, lonely old man).
My parents ensure they come round to see me and my partner when his son isn't there, or I go to see my parents alone (without my partner) if his son is with us for a weekend.
My parents have given me and my partner some sweets/small toys/books to pass on to his son at christmas time, plus my mum has bought a few items of clothing for my partners son (which again was passed directly to us, not given over to his son directly from them ... but he is informed who got these things for him),
so they do the very basics, just to ensure a 7 year old child isn't left out or without anything (which I think is lovely of them, given the very limited times they have seen him, plus they know me and my partner get a huge backlash from the biomum if she finds out that my parents have dared to give HER son anything) ... oh it's all sooooooooo pathetic