If it were me, I'd be at the vet's with Decker the moment they open in the morning. I wouldn't wait for them to open, and call first, I would just BE there.

They can hold him there in a cage, get a pee sample, take him when they have an opening, and you can go to get your dad. They can call you when they know something.

Can you keep him in a room alone over night? I wouldn't be able to do that with any here, so I understand if not possible.