I love all animals, but especially cats.I have also had a dog in the past.
BUT we have some friends where the wife has been brought up without any pets,and her mother instilled a fear of animals in her and her sister. So now she has 2 children, no way would she have pets, even though her OH was used to them as a child.
She will move the children away if she encounters any in a park etc. When they used to come and stay with us, they had to accept the cats, at a distance. We tried to keep them away, but cats are contrary creatures and usually make a beeline for those who don't like them!
Her son actually liked them and wanted to pet them, which we assisted with (they are gentle cats luckily). Now he is an adult and has his own cat, so I'm glad her fear didn't affect him.
There is just no reasoning with people who have that fear.They can't help it. It's best to accept it, and try and work round it if possible. She does sound a difficult person, and unfortunately you have to make the best of it as she is your DIL. I wouldn't try too hard any more, and if possible don't get too upset by her.
The main thing is to see your family in the best way possible.You say you want to show the GC things, just wondered what things?
How about next time you meet for a meal out, you bring some photos of your son when he was a child? Possible not precious originals but print off copies. They may not have ever seen any, and you could tell them some funny stories about what he got up to, what his favourite present/treat was etc.?It might give them more of a connection to you then. Good luck.