BTW when they do the endoscopy the child is put to sleep with a mask first before inserting the IV. That helped a lot for us. We started with my 7 yr old flailing and kicking the nurses who wanted to draw her blood to 4 yrs later her saying , ugh, not again. it does get easier, and in life she will need to get blood work done at some point .
Dee made some wonderful points about prepping her , talk to your Dr's about it.
In addition to StaphanieL list : If you need accommodations for college you will need DX .
In reality you have no idea about your future , where she will be and who's care she will be under on a daily basis and a DX really helps others to reinforce her needs
good luck Maureen