This isn’t a children’s publication but Shades of Romance Magazine, SORMAG for short, has an upcoming Children’s Books (Dec/Jan/Feb) issue. The deadline for this issue is September 1st.
They publish 2 articles on each theme and then other pieces as detailed in their guidelines. These pieces include inspirational pieces called Devotionals (500 – 800 words), fillers which are tips on various things writing related (200 – 500 words), humor, essays, and romance stories.
Query before sending manuscript.
Read the full guidelines here.