C. -
I use Kids First Pediatrics in Highland Village. Specifically, Dr. Conger, but there are others in the practice. Very good staff - Saturday hours, great response times, great with follow up calls, etc. My son loves going - the rooms are neatly decorated and the nurses are great and friendly.
If you are looking at the south end of Lewisville - my previous pediatrician was Dr. Georgulas of Childgrove Pediatrics in Coppell off Denton Tap Road. She was great, too - complete different atmosphere than Kids First - small practice, not big staff, but they'll know you on site after a few visits and the doc is very competent, just not real touchy-feely. We switched due to location and hours.
Good luck -
S. B.