Face painting at public events.. please answer:)?

okay i'm under 18 (14) but for the last 2 years i have been doing face painting at mt little cousins party's for fun.. and this summer i was hoping to do it to make money and do it at field days etc. to make some money.. but i was wondering do you have to be approved by the guards as you are working with children? or what do i have to do? or am i able to do it by approval of the orginisers of the field day etc. this is in ireland by the way :) please answer asap