If someone hires a professional athlete to come and play with their sports team than sure I am completely fine with them earning money for it. If they just go and play for fun out of the goodness of their heart and do not demand pay then I am not sure anyone cares if they are not paid.
Worldwide professional sports is big business, earning billions of dollars for the owner of the teams. TV rights, tickets sales and merchandise revenue are all solid streams of income to both the leagues and the teams. Athletes should be well paid for generating these income streams from the "childhood sports" people are paying to see them play.
Pro athletes should only be paid based on there performance and what teams see as there value in a free market. This leads to a greater spread of talent and leagues become more competitive. This is why the NFL has blossomed into a billion dollar industry. Pro athletes do not deserve to be paid more for sports they played as a child.
I do not think that athletes should earn more pay for childhood sports they played as kids for fun. I think that athletes today are already overpayed for what they do as a profession. That last thing that needs to happen is that they get paid more for sports they played in the past.