Groan... it's hard to know when to weigh in and when not to, yes, Naina007? It's not always as simple as just buttoning one's lip. There can be issues of the child's welfare and safety.
The eye-bathing Iv never heard of. It may be a cultural thing, Idk. But the contamination issue - ugh! - no wonder you spoke up! I hope dil listened.
The kindy thing, idk - sounds more like ignorance on the part of both ds and dil. You were wise, I think, to give them the correct information if only for gs' sake.
But your choosing to just go "book him in" was highhanded, I'm sorry. And the fact that you chose a kindy that was inconvenient for dil (shopping centre or not) - oh no! I get why you did it, but I can also see why dil felt you were "taking over." You were making decisions for her and ds' child - and with your convenience in mind over dil's (the mum's).
I don't think her angry reaction to this was cultural, nor the 2-month estrangement as a result. Imo, many modern dils would have done the same, not just Chinese dils.
Oh wait... I hope she didn't attack you physically - that would be wrong in any culture, I believe. But verbally? We hear that often here. I wish people would be more civil but, as I'm sure you know, sometimes they are not.
It's awful that gs' activities were cut short. That was selfish of dil, imo. Are you sure ds and dil didn't find another way to get him there, however? Isn't it possible they had somebody else watch him on those 3 days and that person took him to his activities?
Anyhow, I take it the two months are over and you now see ds and family again. Are you also back to watching gs? I hope that all is well now. If I were you though, I would try not to go over ds and dil's heads again.
Altogether, you sound like a great mil & gran. I'm sorry if dil doesn't appreciate it.