I love this book
Drawing with Children by Mona Brookes (Paperback - Jun 4, 1996)

it offers practical instruction AND a gentle way of looking at learning/competition.

If your DC actually want to improve their artistic abiltiy, and the confusing 'what is art' question - try this book.

If they just want to complain, I would barter them with 'do x household chore for me, and I'll listen to you complain for 15 minutes'

Smiles,
Grinity

Coaching available, at SchoolSuccessSolutions.com