I put acrylic exts on a girl who was 15 once years ago. When she got home I had her mother phone me up breathing fire at me down the phone. Hard lesson learnt for me ! I would have a chat to the mother always first, it maybe that her 10 year old needs them for a good reason, but I would explain the fact that the nail is developing, aftercare, maintenance, cost etc, I'm sure they would find an alternative.