defnotnanny You definitely cannot take a dog to a house where there is a cat without the house owner's permission. It is simply not fair on the cat whose home it is – even if it has a dog of its own. Your daughter has quite enough going on this time without trying to keep dog and cat separate or worrying about the cat running away and getting lost, run over, adopted by someone in the next street who thinks it's a stray, abducted by aliens, etc. It might not come home this time and your daughter doesn't really want to be pounding the streets, sticking notices on lamp posts and looking under cars while calling "Tiddles, Tiddles" with tears running down her nose. Also, lovely though dogs are, a new mum doesn't terribly want them poking their noses into places where there is a tiny baby even if it is just inquisitiveness rather than aggression.
First, your husband must understand that your daughter's cat is as important a pet to her as his dog is to him. I appreciate that he is unenthusiastic about kennels, especially for an old and needy dog. It looks as if the only solution is for your husband to stay at home with the dog. However, if a neighbour could be prevailed upon to do a little looking after, perhaps your husband could travel to your daughter's, stay overnight and travel home again the next day. This is not an ideal solution but right now the most important people in this scenario are your daughter and soon-to-be grandchild.