Maybe invite them over to your place if they want to see you & the kids, make up an excuse that the kids are happy at home and don’t want to go out, or suggest going out to a park, get something to eat etc rather than it looking like you DONT want to see them just try and arrange something and negotiate
Tell her it’s a lot more convenient if she comes to your house to see your children as everything is already baby proofed. Then you can both relax and have a cup of tea instead of having to be on constant baby watch
Say "I don't want to come to your house because it's like a hoarders house" I had a MIL like that and we said we wouldn't ever stay over. My current MIL's house isn't that bad but they aren't as clean as I'm used to and they have a jack Russell that runs on/over my 3mth old niece when she's on the floor. So we arent taking our newborns there.
I’d ask your husband to talk to his mum about the safety of the house and his concern for her x
Waw that sounds awful, how about you invite her over, or you go for a coffee or a walk instead of visiting her at hers.