Hi there luchino,
It sounds like you're concerned as to whether or not your iCloud info will get downloaded to the phone if you sign into it. It really depends on which screen you are seeing. If you are seeing this screen, then that is iCloud Activation Lock, which is a security measure and will not download anything to the phone:
From: Turn off Find My iPhone Activation Lock
If you are seeing this screen when setting it up, then yes that will download your iCloud account data:
Get started with iPhone, iPad, and iPod touch
Thank you for using Apple Support Communities, I hope your son has a great trip!