To be honest you seem a whole lot more unreasonable now you have revealed this was a reverse. I still stand by the fact that the best solution is to not buy token gifts for any of them, but I think your expectations are entirely unreasonable. This jumped out at me:
He bought extra eggs, though I’ve said that next year he needs to speak to his dad directly to ensure that doesn’t happen again. His family are over quite a lot, so I’m hoping they will get closer to my dc over time.
So his family doesn't really know your kids, yet your partner has you ordering him to ungratefully tell them off for not equally treating your kids as much as his own, who they've presumably known and loved since birth? It comes up all the time on MN, but I just cannot understand how anyone can't see how totally self absorbed it is to expect grandparents etc to automatically view children they barely know, in the same way they view their grandkids, just because their parents are now in a relationship. I'm not a fan of any kind of demands of people when it comes to gifts, anyway, so if I was your partner I would have been absolutely mortified if you had "told" me I had to tell my dad that the gifts he bought for my kids, and the tokens he kindly bought for my partner's kids, were not good enough and he was an arsehole for not treating them all the same. It sets up a tone that the gifts are an expectation and a duty, too, rather than just something affectionately given by one loved one to another, which I think is really rude.
I've never known anyone do something like the Easter Egg thing maliciously to "make a point", he probably just didn't get them a big present because you know, he doesn't really know them and genuinely doesn't see it as his responsibility to treat them like his grandkids. He's just a kindly adult who occasionally sees them. He probably thought he was being nice by getting them something even though he doesn't have a particularly strong relationship with them, which in my opinion, he was. If I were your DPs family and I was getting these telling off's, it would really put me off getting to know your kids better as you hope they will. I think going in with a load of demands and expectations of people because of your decision to blend a family is really entitled and damaging.