I Like your ex husband and as someone with CAH : ) his concerns are valid and I do understand where you are coming from as well.
For me it is the whole name of this the Natural history Study or whatever and to me that is a bit much.
Maybe you approach this as hey hon this is nothing more than a really good second opinion on our kids health.
Also, you have to be able to handle that as your ex feels that this experince might have negative consequences in the future as going through more testing may cause more stress in other ways. There is no amount of playing with toys or doing crafts in the waiting room that makes up for what goes on in the exam rooms.
If there are students that follow the Doctors even just one then consider how it feels to be put on display.
I know the $rap that I went through for CAH at the best University/Hospital didn't do anything but make me a Lab Rat.
and I did school in the hospital too .......ummmm when I went back to my own class and own school I felt like the outsider with the medical problem.
Good luck with all this and you mean well.
aimee