Was your son able to use the fitness center on your cruise? Im in a similar situation, my daughter will be a few months shy of 16, she just needs to use the treadmill for 2 mile runs as part of her summer training for soccer. She is very serious about her training and will not play around. Her mile has to be under 7min, so we wouldn't need the treadmill for very long each day. I know I have to be prepared to leave, but hope she can get her runs in.