Dont feel comfortable leaving our baby with in-laws?

I'm pregnant with our 1st child, my partners folks are lovely people and are so looking forward to meeting their grandchild. Their other son and his girlfriend are also expecting and due 2 weeks after us and have already arranged for them to childmind their baby once a week when they go back to work after maternity leave. At present I'm not sure if or when I'll be returning but if I do then they're keen to extend the same offer of childminding our baby too. This is a wonderful offer as chidcare is so expensive....BUT....they have 2 small dogs and they're utterly unruly, they have the run of the house, they pee everywhere and chew everything, are always jumping up and jumping all over the furniture, the house is dirty with dog hair and slobber and I'd be really concerned about our baby being there, but how on earth do I even broach the subject with my partner if it comes down to it that I need to go back to work that I'd rather our baby went to nursery without offending anyone?