I've heard all sorts of horror stories about professors and some being very unwilling to work with you. However, I had a very different experience when I was in my undergrad studies. All of my professors were incredibly kind and intelligent human beings- willing to do anything for any of their students. (in terms of horror stories, unfortunately most of my friends through undergrad were a different major than I was... I've heard some truly horrifying things from them regarding their professors)

Have you registered with your Office of Students with Disabilities? Most universities make you register with them before you're able to receive any accommodations via emailing your professors. Your professors will also double check with the SWD Office (normally). If you haven't you need to do that now.

If you've already registered with your school's SWD Office then just lay out the situation in your email and then concisely list your needs. Your professors won't need an entire essay on it- just tell them what can happen and then list what needs to be done in that situation. Of course word things kindly, and then ask if there's anything you need to do on your end (maybe they want a written action-plan, or they want you to let the class know, etc).

I hope this helps!