Hi, I actually took all of those pre-reqs at ENMU! I chose it because it was the cheapest I could find, plus it had all the classes I needed and I didn't want to have to mix and match and have even more transcripts to send in. The most I ever took at once was 3, and that was pretty stressful, but I was working part time - if you aren't working I think you could do it, but I wouldn't go over 3. Just make sure to stay organized to not miss any deadlines. Over the summer I took 2, intro to comm disorders and neuro, because I tried to balance a less demanding course with a harder one.
I would say of all of them, anatomy was the toughest course for me. It was definitely the most demanding in terms of assignments and projects, instead of just quizzes. And her tests were pretty hard. Neuro was hard too, but she repeated questions a lot from quiz to quiz to really drill the info in, so the final wasn't too bad. Audiology took a lot of time and was on the harder side. Intro to disorders and phonetics were probably the easiest so if you are going to do 3, you might want to include them. Language development was a lot of info but (to me at least) more interesting and easier to absorb than the more science-y ones!
The courses were all completely online and neuro has been the only class that required a proctored exam (just the final, like tvl said) BUT you can take it with an online proctor - basically you just take it with your webcam recording you.
The way the courses are run totally depends on the teacher - some had no lecture component at all, some all lecture, some in between. I would read ratemyprofessor reviews before picking if you have the choice. Some were definitely more helpful than others. If you have any specific questions feel free to PM me!
Good luck!
PS - I just re-read that you need to take 5 all this summer... I don't actually think they let you take more than 4 at a time, so you may need to combine schools if you need to do all 5 - maybe you can find another school that has a slightly different schedule so they don't all overlap