Well, gotta put my 2 cents in here. I was 25 and a working professional when I got my metal braces. I actually MISS them! Yep, there is something about them that make you look younger, and in your case, that may be what you're trying to avoid. I, however, was flattered when people thought I was 18!
Once I had them removed, my orthodontist molded me for a "bite guard", which is basically the same thing as the invisilign. (It served as a retainer, of sorts.) I'll tell you, I will NOT be seen in public with this thing in my mouth! True, you can not see it on my teeth, but it MAKES my teeth look HUGE! Just a thought!