For example, a childlish or playful boy or girl with the help of your prayers and encouragement could become a firefighter or a teacher. Do you sincerely your prayers can do this?
I'm going to tentatively answer "No", but with the caveat that I'm not confident I understand the question or its point.
We should pray for the best for our children. I don't think we should presume to know what that is specifically.
"Our Father... Thy will be done," and not our own will. His thoughts and ways are higher than our thoughts and ways. Pray that the child will grow up healthy, strong in faith, and desiring to fulfill God's plan for his (or her) life.
I don't believe prayers should be used to 'get what we want' as much as they should be used to ask for the things that will help us live this life, like strength, courage, patience, tolerance, and gratitude for what we have been given already. God isn't a dispensing machine.