On your wish to appear professional; I once, early on when a parent arrived for pick up looked down at my pants and shirt...a mess with paint, dirt and chalk and apologized to the parent. Without issuing a beat she said "I would wonder if you all didn't look that way at the end of the day, it shows that they are having fun!". As long as you're not wearing ratty old things with holes in it or flashing the parents...I honestly don't imagine the parents even care what you're wearing. Your professionalism will shine through in the other things you do day to day.