Sounds like I'm a day late and a dollar short here - I'm guessing you already have much of the info that you wanted about retinoids.
Just a few add ons:
See some of my thoughts on an earlier post about my experience with Accutane: http://www.ichthyosis.com/ubb/Forum3/HTML/000009.html
I think of myself as having lamellar; however, several of the dermatologists on the Foundation's Medical Advisory Board put me somewhere on the spectrum between lamellar and CIE - they definitely don't put me solidly on either end of the spectrum. So, perhaps you could consider my experiences at least partly indicative of what someone with CIE would experience.
As people have already said, whether to use a retinoid is an intensely personal decision (for you as a parent or for Jordan herself). The best you can do as a family is gather as much information as you can and make the most informed decision possible. And then continue to periodically re-evaluate your decision, whatever it was.
Mary Spraker is an outstanding derm who is well known for having expertise in ichthyosis. She's been very generous with her support of the Foundation for Ichthyosis. She's a very good physician, from whom you should expect excellent information and advice.
Please also keep in mind that not all retinoids are created equal: there are some differences between Accutane and Soriatane, and not just in the half life. So try to keep the info that you here about each drug distinct in your mind. Some info is true of all retinoids, some is very specific to which particular drug.
Take that for whatever it's worth (that and a $1.49 will get you a cup of coffee, as they say),