For children its tough to maintain a gap between juice and meal. Can they drink juice along with meal? or can they drink juice in the afternoon?
It is best to have juices empty stomach in the morning, at least 1 hour before breakfast (even for children).
If it is not possible to do so, you may give them the juice in the evening (about 2-3 hours after lunch, and 2-3 hours before dinner).
However, we do not suggest drinking juice along with meals (even for children).