It strikes me that some posters are more indignant about what the grandparent's said, than the OP herself. I think now that she's had the opportunity to read some other opinions, she's realised that actually the GP's weren't being as unreasonable as perhaps she first thought, bearing in mind that she says that she too is 'shattered from it'. There are also people here making things up as they go along, they didn't send a nasty text afterwards, they told the OP as they left. Come on people, read the thread if you're going to comment and stop trying to wind things up.
Now that we know the full story, I think the grandparents were probably tired and cranky themselves, having done a fair amount of travelling, being away from home, (so probably not sleeping well), and having put up with tired, cranky, little ones for several days, so they then made the mistake of jumping in and saying that they would only do video calls until the kids are bigger as they left, which naturally upset the OP, as she'd been kind enough to host them. Perhaps if they'd waited until they got home, and had had some time to relax, they'd have put it to the OP, a few days later, and she would have been more understanding and less upset in the moment.
Personally, I think the whole thing is a storm in a teacup, and being almost the same age as the GP's myself, think that no one really thought through what was going to happen over the holidays properly. Now that the GP's have had their memories refreshed about what toddlers can be like to live with for more than a couple of hours, and how excitable and overwrought they can get over Christmas, they've realised it's all too much for them, and have perhaps overreacted, but a good chat and a bit of thought, can, I'm sure resolve things until the kids are a bit older.
As a matter of interest OP, is there any reason why you didn't actually put the kids to bed for a couple of hours if they were over tired? They might have fought against it initially, but perhaps if you'd asked Grandma or Grandpa to sit with them while they dropped off, it might have helped everyone. Just a thought.