A child unfortunately has no discretion whether s/he wants to visit a non-custodial parent. There is a court order, and it must be abided. Should you want your son's opinion to be considered in the event you file a Request for Order (or Order to Show Cause), being 15 years of age the court may consider his opinion in chambers, and it must be requested ahead of time. It is within the court's discretion whether or not they will have your son's opinion heard. In short answer, "yes," he has no choice but to visit non-custodial parent, or otherwise a contempt action can be filed against you.
I suggest you consult with an attorney in your local area for additional advice on your particular case. You may visit our website at www.lavifirm.com for additional information.
Attorney David Lavi
Family Law Attorney
Los Angeles Long Beach Van Nuys Norwalk