Legal requirements for massaging teenagers

I am a holistic massage therapist from England now working in the Netherlands for the past 6 years. I want to create a massage clinic focussing on supporting teenage girls. What are the legal requirements / protocols that i need to work with girls aged 12 - 18yrs old?

I am insured with Balens EU and UK.

I would like to work with local government in Utrecht eventually once i have what i need to officially set this clinic up.