A.J.
We use Pediatric Associates of Dallas. They have late hours (open until 9pm I think) and they are open on saturdays for sick kid appointments. They have their own lab and x-ray there in the office so you dont have to go over to the hospital to have tests done. We were not with them to begin with and I had to take my 4day old over to the hospital to have blood drawn in the middle of January with people coughing all around us. Not a pleasant experience.
Good luck!