One thing to make clear though. Dont just take him there saying its all beautiful and clean. You know even Nepalese returning to Nepal after few years gets overwhelmed by pollution , crowd, dysfunction of rules and regulations. So, show him the bad side as well so he can get prepared. I have heard similar case where someone took his American buddy to Nepal and after he returned he didnt speak to him because he was misled by the Nepalsese friend. He was mad that Nepal was so dirty and chaos. Also, I wouldn't stay in Kathmandu since pollution and overpopulation might make him frustrated and end up getting annoyed with you as well. Go to Annapurna Base Camp, trek for few days, stay in Pokhara, Chitwan. So, just be honest about pros and cons and let him figure out if he still is up for the ride.Good luck!