HI this is Richard in the UK. I am not sure of anyone over here doing a paeds private practice service in the physio profession. However I work with an osteopath who does extremely well out of treating kids. Also the chiro's are pretty clued in on private paeds work. I suppose the answer to your question might be that, No, there aren't many doing it privately. Hence I would see it as a great opportunity. Bets of luck
Richard