I wouldn't wear scrubs on a 1st meet and greet. I had to interview a H.H.A once and she wore scrubs I thought maybe she couldn't take the time to wear "normal" clothes at least just once....I would wear something nice and causal like nice khaki maybe a nice blouse..
Just dress casual and be yourself. be confident and let the parents know that you will take great care of their child in their absence. Keep a smile in your heart and know that you are the person for the job =)
Id wear a pair of slacks and a button up collared shirt, a nice necklace, small earrings, and a cute pair of low heeled closed toe shoes. Soft neutral makeup (easy on the eyeliner and lipliner). NO perfume. And neat put together hair.