Fenix 6 series - Can my family track me while hiking without cell coverage by using the GPS and the Connect app?

No unfortunately.

The best explanation I ever got on this topic compared the cell phone to the fax machine. I know it’s old school, but it resonated with me. If you have the document and the phone line, you still need the fax machine to facilitate the transmission. That’s what the cell signal does. Facilitates the transmission. 

The Garmin InReach device does exactly what you're looking for, and it even has a widget for the Fenix 6 so you can send and recieve messages on your watch via the Iridium Satellite network. I just got an InReach Mini last month and absolutely love it. Depending on the service you buy, it can also send tracking points and draw a map for your family at home, I have mine set to send my current position every 10 minutes.

It also has the added benefit of an SOS button that will send a rescue crew to your current position. You can even buy inexpensive insurance with it that'll cover the cost of the rescue mission.

oh thats super cool! is it working well?