Have you considered a reputable, popular tattoo and peircing place in your community?
The be by far the cleanest, professional, and know the most about whatever questions you might have. Any sucessful(not backalley) place will uphold and maintain without fail extremely high standards in reguard to the peicing. For a place like that this is their chosen profession for which they have a lot of training and experience. They are not a teenager working at a boutique to get a discount on jewelry.
When I got mine done, as well as when my daughter decides she wants hers done, I will do both at the same time. Why having the impending nervousness of it more than once, you don't want her to freak out with the second one becuase the first one hurt. I think most children are typically done at once to avoid any struggles
I would call to see if you need an appointment, and say the age of your daughter and the intent of doing both at once.