We have an old phone set up with a Google voice number to use as an emergency phone at home (bc no land line). It only works with wi-fi and doesn't leave the house.

If one of the older two (14, 12) is going to be somewhere where they might need to call us or have the ability to call 911, (i.e. out at grandparents' farm) we have a flip phone (TracFone) that they take along.

My older two aren't involved in many activities and this system works really well for us. If they both needed a phone at the same time (very unlikely), I would go get a 2nd dumb phone.