How do you safeguard your phone.

I love this cell phone lanyard! I attach it to my cross body bag and then don't have to worry about dropping it, leaving it somewhere or have someone swipe it. The cord is long enough that it doesn't interfere with taking pictures or tapping when I use Apple Pay. Your son and his friends could attached it to a belt loop?

https://www.amazon.com/dp/B09YM1SX6Z?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

I use a neck lanyard long enough for me to keep my phone in the front pocket of my pants. I advise against keeping phones in their pockets without a lanyard. Too easy to fall out while hiking and easy access for pickpockets while in cities.

I put my flip phone in my front l pocket. Fits pretty deep. But I don't often go to high crime destinations or go mountain climbing. If I did, not sure what I would do. Good chance your son won't wear a phone around his neck. Maybe Kathy's idea or cargo pants. When I fish i have a water proof bag/lanyard around my neck.

Remind your kid to NEVER set anything of value like phones, wallet, sunglasses, ... on a table. When everyone is busy chitchatting, it's easy for someone to quiet lift the item without anyone being aware.

Also, no leaving jackets and bags unattended while stepping away for a second to grab a straw or something. It may be okay at your local McDonald's, but not in Barcelona or Rome or ...

i have this one, similar to the other mentioned. https://a.co/d/hZlFDeY

Keeping your phone in your pocket is totally fine, I don't see the problem. I would definitely recommend a phone case and a screen protector but you don't need anything more than that.