All good suggestions ladies. I think I will try some with the dried fruit on before I bake. I would like to pipe a few features on too (you know, sleeves etc) but it needs to be something that will harden so the jams, blended fruit etc are out.

Glamourcide - I was thinking I might experiment with a mix of cornflour and a little icing sugar and see how that goes. It would need to taste ok too, or DS won't eat it!

Lenny - DS doesn't have any intolerances, but I do like to make sure that what he eats isn't full of crap, iykwim. That's why I'm ok with him having a little icing on top as a treat.

My only other thought was melted dark chocolate. I know it's got sugar in it, but it surely can't be as bad as pure sugar (aka icing sugar).