A TOWL would be good. That's probably the best measure of written expression currently available. I'm still a little curious about a real speech and language evaluation, but a genuine writing disability should show up on the TOWL, which is good enough. One of the handy aspects is that there are multiple subtests, breaking out various aspects of mechanics, sentence structure, and applied open-ended writing, so it should be possible to see if there are vulnerabilities in specific skills and/or when skills are combined.
