I think you have a solid plan, especially if you have time to devote to study. I took Anatomy, Physiology and Micro at the same time and did well because no kids no job, just DH.
We covered a fair amount of the immune system in micro as well, but what you need to know should be covered adequately within the class, if you have a decent instructor. I think that anatomy is a good one to take with micro because it's memorization based while Mirco includes a lot of processes. Taking micro and phys concurrently is strongly discouraged by my instructor, especially for those with kids & jobs.
There is crossover between the classes, but they should just reinforce each other, regardless of order.
My biggest suggestion, for people who have time, is to take medical terminology
because it REALLY gives you a good base of knowledge for all the scientific/medical language.