My Nan keeps pressuring me to bring the dc round to see her (once lockdown has finished)
She used to drive and would collect them every Saturday but recently got rid of her car.
She also moved a few months ago with brand new carpets and everything. However, the house absolutely stinks of dog wee. It is smack in your face stink to the point where after 10 mins, it’s stuck to your clothes and you have to wash them and shower 
She has 3 dogs and 3 cats and before she moved, it was never this bad.
She has her son living with her so it’s not the case if she can’t clean up.
Dd is also allergic to cats which can set off her asthma, but when I point this out, she just says “but she used to sleep over before”
But before, the cats didn’t go upstairs, the house was bigger and there was hard wood floor.
Now she’s in a bungalow, there’s carpet everywhere and the cats all moult.
I know she will take offence if I say the dc can’t come round because of the cat hair. She doesn’t believe dd suffers that bad 
But the house smells that badly, I can’t let my dc go round there.
If I suggest meeting out of the house, she won’t like that either.
How do I say “sorry nan, my kids can’t come round” in a way that doesn’t upset her?