Son traveling over seas

Does he need to use the phone? If so, best to get an international plan. Either the $10 day pass or a passport plan. If he doesn’t need to use his phone, you might be able to remove international roaming from that line but can’t guarantee that will work. You can also instruct him to leave his phone in airplane mode and only use WiFi. 

You can turn off his data on your account.  Ask him not to make calls or send texts unless it's an emergency.  If an emergency comes up, you can add travel day pass on his line. 

Thanks so much. I really appreciate it! I did these things and his dad is going to make sure he keeps it in airplane mode so he doesn't use it without wifi. Thanks again!