I used to work as a research study coordinator and I don't think you have anything to be worried about. Read the consent form, there should be notation of how your data will be stored, identified and used. Anyone who does research has to have their protocols approved by an institutional review board (IRB), which exists to protect the privacy and safety of study participants.
I would ask what kind of information they will give you about the data (genetic and otherwise) that they gather on your kids. Some studies will give participants lots of information while others do not.
There are several known genetic markers for dyslexia. I had my DNA and my son's DNA tested by 23andme.com. I have one of the dyslexia genes and am dyslexic, my son does not have it and is not dyslexic.
