1 you don't have to be any age to cast a spell or do a ritual. And wishing for someone to adopt, I mean that's you wish. To be honest magic doesn't have a color. You can use black for good and white for bad. Or however you want to say it
Never think it is black magic to want to be adopted into a family to love and cherish you. I pray that your spell is answered because you are a beautiful soul wanting to give as well as receive love. Remember love is the most precious gift to give anyone who is willing to receive and cherish it.
My prayers to you.