Thank you for your story.
Talk with your Son about what you can and cannot do with an Apple Watch.
You will need an iPhone XS, XR, SE 2nd gen, 11, or newer. An older iPhone will not pair with the current generation Apple Watch.
If you get a GPS Only Apple Watch, then you need to have your iPhone nearby, where nearby is generally in the same moderate sized wood frame constructred house. As long as your iPhone is nearby, you can do EVERYTHING with a GPS only Apple Watch as you can a cellular.
If you get a cellular Apple Watch, then it shares your iPhone's phone number, and cellular carriers that support the Apple Watch add a $10 U.S. fee to your iPhone bill. The cellular model will allow you to leave your iPhone at home when you go for walks, bicycle rides, etc...
These are the cellular carriers that support the Apple Watch
Apple Watch - Carriers - Apple
NOTE: For the GPS only models, your iPhone cellular carrier does not matter.
Things I do with my GPS Only Series 4 Apple Watch (I almost always have my iPhone on me, as I stopped worrying about bulges in my pockets years ago, or very close to me):
• It tells time, date, day of the week
• Every iPhone alarm, appears on my wrist, where you can acknowledge it, dismiss it, etc…
• I like the iPhone 3rd party “Alarmed” app (http://yoctoville.com), for my alarms
• Ring.com door bell can display a static image on the Apple Watch
• Weather (this gets used a lot)
• MyRadar 3rd party app will display radar image
• MyRadar and WeatherBug 3rd party apps will send you weather alerts
• Make/Receive phone calls
• Make/Receive FaceTime audio calls
• Use Walkie-Talkie anywhere on the planet
• Silence phone ringing by pressing the digital crown (great for SPAM calls)
• Send & receive iMessages
• Send & receive SMS TEXT
• Say “Hey Siri, 14 and a half minute timer”
• Say “Hey Siri, remind me when I get home to do xyz”
• Say “Hey Siri, message my wife/husband/Susan/George/etc…”
• Say “Hey Siri, start Outdoor Walk”
• Say “Hey Siri, end workout”
• Use a 3rd party garage door opener app and device (such as MyQ)
• You can check your calendar
• Read your email
• If you need to take an iPhone picture where you cannot see the screen, use Apple Watch Camera app as a view finder/shutter release
• 3rd party Ocean's Tide app for beach visits
• Hand washing reminder and timer
• Unlock your Mac (I do this several times a day)
• Unlock your iPhone when you are wearing a mask
• Track your exercise and physical activities
Since my Wife got her Apple Watch, we have been able to reliably iMessage each other, as she never keeps here iPhone on her person.
If my Apple Watch was lost, stolen, or broken, I would order a replacement as fast as possible, as I would miss it so much.