Where are your students in the range of English skills: just beginning (a few words, very limited understanding), middle (have Basic Interpersonal Communication Skills BICS--can understand and talk playground), or advanced (Cognitive Academic Language Processes CALP)? Lots of ELLs sound like they know English, but the academic language defeats them.
You might want to do some Interactive Writing--sharing the pen. You and the students come up with a sentence (I pencil it in the corner of the chart paper) and then write it together word by word with the students supplying the letters/sounds or words they know and you filling in other parts.
These kinds of group stories model what is expected in writing a story, give the kids skills in stretching the words to hear the sounds and provides a safety net while they learn.
There are several good Interactive Writing books to support you. Try Fountas and Pinnell's. They have lots of ideas. You might also try the Writing Fix web site (I can't get the URL to come through here and/or
http://www.stanswartz.com/IAW%20excerpt.pdf
I'm wondering if your kids would do a better job with a story frame or writing variations on a story that is read to them. Perhaps a variation on Brown Bear, Brown Bear or Mary Wore Her Red Dress.
Story frames would be along the lines of
I wish I had __________.
I wish I had __________.
I wish I had __________.
but I do not want __________.
My monster has ___adj_________ teeth to ___verb______.
My monster has ____________ eyes to_____.
etc.