Here are two very lovely Irish based magazines seeking for writing for children.
The Caterpillar - a sister magazine of The Moth. Seeks poetry and short stories, for more see here
The Looking Glass - produced from Trinity College Dublin. It is seeking submissions for volume 3 issue 1, of short stories, poetry, novel extracts, illustrations, and comic strips. Deadline 01st March 2014, see details here
Also for children, UK based publisher Chicken House are running a 24 hour submission opportunity for unpublished children's novels aimed at ages 8-12. The crucial date is 25th January 2014 and further details of sending five chapters and a pitch of the novel are here
Good luck in submitting to any of these.