I taught my 3 dc without an instructor, they did an under 17 driving course on an airfield though so could drive, reverse and do maneuvers though which is what I would expect an instructor to teach.
We started on a quiet, wide road. Practising starting, stopping, pulling away so lots of mirror, signal, maneuver. We introduced reversing around a corner and turn in the road to build confidence and only moved onto a busier road when they were ready.
Some things that helped me- a stick on interior mirror so I could do all observations, avoid giving feedback in the car other than brief instructions so "watch your left", "brake" "think about gears", etc. Keep it positive, lots of affirmative, so nice "gear change", "good use of mirrors", "well done on spotting pedestrian", etc. Be calm and debrief afterwards.
Remember that if needed (emergencies only or they get cross), you can pull up the handbrake or knock the gearstick into neutral to slow or stop the car.