50mm f/1.8G perspective distortion for children's portraits on DX?

Can anyone tell me if there will be perspective distortion from a 50mm lens on a DX sensor for children's portraits? My children are 6 and 3 years old, maybe about 3 to 4 feet tall, I think.

I believe that for a 50mm lens, trying to capture 1.5 feet of my kid (approx upper half of my kid), I would be about 3.1 feet away, if I'm calculating correctly.

Thanks!