Potty issues

Hi, everyone. I am not new to owning dogs. In fact many years ago I bred Rottweilers.
This is my first experience with a small dog.
He is a 7byear old Yorkie. He's a perfect dog except for one thing.
He won't think twice about going to the bathroom in the house. We walk him 2 -3 times a day. He isn't crate trained. But we have grandchildren and we have a large corral ( it's a big, fold up one to set up a quick area to keep the kids in. ) when He's in there he will hold it. So we know he can hold it if he wants. But if we leave him alone for awhile then all bets are off.

So I would like any suggestions 🤔 that the community will come up [email protected]
Thanks