User should be able to start a root-program

Hello, I have a program that runs a root (the program also starts child-prozesses as root). Now there is one user who should be able to start/stop this program. I have tried to give the program-file the s bit -> the users was able to start the program but then he receives a error that the start of the child-prozesses is forbidden. Is there a posibility to start the program without root-rights? Thanks Martin