So I made cupcakes last night - basic recipe doctored mix, extra egg, pudding, milk instead of water and when the cupcakes were cooking, they got dry on top!
The inside was nice and moist, but the outside was dry and they weren't even cool yet for me to put icing on.
I don't know what icing you're using, but the oil from most buttercreams would fix that little problem right up.
April is probably right; the bc should help that. But if you're still worried about it, brush on a bit of simple syrup before you ice them and that should take care of the dryness completely.