i wouldnt force him to go, but i would present him with the option of going, explain to him that he can talk to the councillor alone and whatever he says stays in the room with the councillor, and you wont know what is said unless he agrees for the councillor to tell you.

presenting this option will show him you are not treating him as a child but has an adult, we has adults all know we have to make choices that we sometimes dont agree with but it is for the best.

good luck