Where does encouragement stop and pushy parenting begin?

We’re at dilemma point with Ned (who is 8 in January) over his guitar playing. Like most of our children, practice is seen as a chore to him. In the past we’ve dropped the boy’s guitar, and Fifi’s guitar because they didn’t practice enough (the boy doesn’t practice his drumming as much as he should but is still heading towards grade 3 with speed, and Fifi is just about doing enough piano practice to justify continued lessons). The problem is, Ned doesn’t play anything else, so it’s not as if he is doing something badly while doing something else better.

We’ve talked about it with his teacher, who is great, and is also MY guitar teacher (I got a guitar for my 40th and am slowly but surely learning to play it), and he says Ned would regret stopping because he’s learnt a lot but there is no point in him continuing if he’s not going to put some effort in. As Ned and I have consecutive lessons on a Saturday morning, I thought this would mean that we could practice together. Well, I spent most of last nights masterclass by Arsenal (I don’t get to write that very often any more) learning how to play Wish You Were Here: