Gampywabbit a friend suggested using the Lina Ng books, so I bought Theory of Music made Easy grade 4. What a difference! Clear instructions and child friendly. Much better than the ABRSM books. Only problem is they don't have answers, but in fact I've found it forces me to look more closely at what he's doing, so I'm learning it too!
DS was going to take grade 5 theory in Autumn but I don't think he'll be ready so I'm switching to Feb/March 2014 entry. How old is your Dd?
Have you found anything good Suki? Dd is at the end of abrsm grade 3 theory book and we are aiming for her to take the exam in Autumn 2013. It would be good to have something extra to keep the practise up over the summer.
ds2 used the Trinity workbooks up to grade 4, they're better than the AB ones. Then used memrise to learn ALL the musical words (then was offended when he was only asked something really easy in the actual exam!)
He generally found the theory quite easy, so didn't need to do much extra practise: just had a couple of composition lessons with his teacher.