Let me answer your second question, which will then lead to your first question.
Part-time programs typically do not offer a significant advantage to career switchers. In your case it'll be even harder for you, because you've owned your own business, so while it may indeed be very successful, your resume does not have any recognizable corporate "brandnames" that a recruiter might potentially find attractive.
At the same time, Georgetown's full-time program is hardly the best diving board to use for a career in consulting. Don't quote me on this, but I'm fairly certain that some of the top 10-15 firms don't even recruit there.
To summarize: go full-time now, if a job in mainstream management consulting is what you want.
What you have going for you: a good GPA, and entrepreneurial experience that is attractive to some schools like Haas, Sloan, and Tuck.
What you have going against you: you may already be over the median age, your GMAT score could be higher.