My English Language Learners have the hardest time with idioms. In order to help them out, I created this simple little booklet where the kids can illustrate the assumed meaning and the real meaning of an idiom. Download your free copy from my blog – Raki’s Rad Resources. 
I love teaching idioms – and you're right, it especially is a struggle for ELL learners.
Thanks for sharing!
~Jessica
Joy in the Journey