Petco again!

Yesterday afternoon we once again I tried Petco. I don't know if it's because Quinn has bad associations with the place, but he was really wound up. It wasn't hugely busy, there were maybe two dogs in the whole store. He started barking as soon as we pulled into the lot. He saw a GSD being walked out of the store and lost it.
I just spent time with him in the crate (door open) and used the clicker, clicking for calm behavior and just letting hang out in his crate.I pulled him out of the crate and he was happy calm while he pottied, but as soon as we got into the store he barked at a store clerk, at Alicia with Sage (her puppy, who's currently living at my house while Alicia's pet/house-sitting).
I did get him to calm down a little, but he was on alert the whole time we were in the store. There were a couple of kids with a small white dog running around. He was focused on the boy when he saw him, but only barked at the little girl with the dog. He's never been comfortable around children, so I'm okay with his behavior at this point.
The worst reaction he had was as we left the store. A woman with a large black mix of some sort was getting out of her car as we approached my car. Quinn began barking, I corrected him, but it didn't help he continued to bark. Her dog was on a flat buckle collar and started to drag her over to Quinn. I just grabbed Quinn by the scruff and turned him away, he didn't stop barking, but the woman was able to get the other dog back under control and they went into the store. As soon as the dog was out of sight, Quinn calmed down. At that point I just crated him.Overall better than the last time we went to Petco, not as good as he's done at Petsmart or the club.