@Carolyn696 are you declining inquiries or requests? For an inquiry, all you need to do is reply with a message. You do not need to pre-approve or decline.
Your listing text says "Our house is reserved predominantly for families with children." If you do not want to rent to anyone else I would change it to "Our house is reserved exclusively for families with children, with no exceptions. Please do not request to book for any other type of group, as we will not be able to host you."
Then, if you still get requests to book from other people, you can reply with something like this: "As noted in our listing, our house is reserved exclusively for families with children. Since you are not a family with children, we will be unable to host you. Because Airbnb penalizes hosts for declining requests to book, in X hours I will accept your request with the provision that you bring children. If this will not work for you, please withdraw your request now to avoid being charged for a reservation you cannot use."
As a side note, I think this requirement will continue to be problematic for you. It's an unusual one that on its face seems pretty arbitrary, and doubtless frustrating to well-behaved adults who don't happen to have children. It might be better to think about your requirements in terms of the behavior, rather than the identities, of the guests.
Also, you have, in my opinion, way too many house rules. I don't think anyone will read them all, so the important ones will be missed.