Hello there Michele!! Welcome to T4L!! OK as a mama of a now 15 year old boy with ADHD, I feel like I have some advice that might be good for ya!!
FIRST thing is patience, I am sure that everyone says it but with a kiddo that has problems concentrating it is a must!! I have to tell you that T4L worked wonders for us that first year, he loved cartoons so he was learning and having fun again. Sometime he just wasn't able to do in the system! He also came home crying and pissed about himself mostly that he couldn't get done with the work in time like everyone one else. Now I still do some timed tests to keep him prepared for when he takes classes else where he won't totally melt down. I think T4L will be a great fit for your son, especially since you work! You can assign him so many lessons for while you are gone and when you can spend more time with him make up some lessons in something that he loves to know more about! For us it was animals and video game design so that's what he does on his own now!!
Second I would suggest finding out what his learning style is... my son needs visual and hands on activities to make him retain his studies. So I incorporated sites like Spelling City for his spelling lists, where even now he plays a game to practice his word list!
I would also suggest hooking up with others from MO in our MO state forum for anything to do with MO requirements for homeschooling, hope to hear more from ya!