Will my older cats ever warm up to our new kitten?

No, not safely. The vaccine is - at best - only 80% effective in preventing the disease. That means your vaccinated cats have at least a 20% chance of contracting it from contact with her.

FeLV is highly contagious.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.