Naive of me but I let mine compete for whatever position he desires to play with the knowledge that ultimately the coach will place him where it best benefits the team. On occasion, those positions are one and the same on other occurrences they have not been. Competition among the boys will drive them to excel and things sort themselves out.
As a parent, I question any other parent who comes in demanding or requesting a specific position(unless maybe its a pitcher or catcher). Successful coaches and organizations know how to put players in the best position to succeed which ultimately helps the team. Making these requests puts kid before team and to me that is wrong but.....I am naive.