Read the "Out of Sync Child" before meeting with therapists who will be doing the testing.
It will give you things to consider and good foundation so you can ask good questions. It may also give you insight into your son's behavior.
See:
http://www.amazon.com/Out---Sync-Child-Recognizing-Proces...
Also check out the following for some tips that may help make mornings and daily communication smoother.
http://www.amazon.com/Organizing-Disorganized-Child-Strat...
http://www.amazon.com/Late-Lost-Unprepared-Executive-Func...
Last but not least, if keeping on task is a big issue, and not following through when asked to do something, you may want to try not giving choices for a while as others have suggested.
Do not listen to those who say he is playing you or this is some sort of power struggle. You can tell the difference. From what you describe, it sounds like he may truly have a focus or sensory problem. If there is a focus issue (based on what you share) choices make things overwhelming and to those who don't realize what is going on, can seem like they are being difficult or are not listening...when quite the opposite is true. They are just struggling with processing the request and executing it. Stay patient, and make things easier by keeping requests simple, and definitely offer no choices for a while and see if that helps a bit.
In the morning, have his clothes ready, and the night before go through his school bag with him to make sure assignments are done, packed and ready for the next day. Do whatever you can do to help him stay on task. It should get better.
If you could make a simple to follow through on, duties chart with pictures and set a daily routine that doesn't change, that will help him alot too.