Contact your local law enforcement and arrange to have your criminal background checked. This will tell you what is on your record. If you were never convicted then you should not have a felony on your record.
Lots of factors need to be weighed in this situation. When will your son turn 21, what court is the case in, the officer's report and experience level, whether the roadblock was legal... and so on. You really owe it to yourself and your son to discuss this with a seasoned DUI defense lawyer. Good luck.
You indicated you had a lawyer. You need to discuss this with you lawyer and develop a plan for going forward. You do not want to have to travel back and forth from CN to Atlanta more than once if it can be avoided, However, that does not mean that pleading guilty at arraingment is a sound decision. Again, please discuss this with your lawyer.
I am not clear on what you mean by "deprivation of rights" but it seems clear that you have several defenses to the charge. Since you have counsel, make sure to work with your attorney to maximize your chances of an acquittal.
DUI charges are very difficult to exphunge in GA. If you are confident the charges wil indeed be expunged and have some timetable for the process...you would benefit from waiting until they are expunged to apply.