I agree Waz, I reckon you've just got to keep it low pressure. I'm not much of a guitarist either, but I know enough to get them started.

I began by just teaching them a few simple melodies/bass lines from songs that they already know. Being able to play something you recognise is a good motivator. Then I don't harp on about practice, but rather when they are bored or being forced to have non-screen time I just suggest picking up the guitar for a bit. My middle daughter now knows how to read tabs and has been teaching herself what she wants to learn - which at the moment is the harry potter theme music and Rip Tide.

It's got to be fun and relate-able. When I had been playing for a couple of years as a kid I decided to try lessons again. I really wanted to learn blues and rock, but my father told the teacher I wanted to learn classical. So I spent a miserable year and half with that teacher slogging away at stuff I had zero interest in. Very nearly turned me off completely.