I think the foundation of your decision should be based on whether or not you will be wasting the Dean's time.
They're incredibly busy (especially in the middle of an application cycle), and you don't want to come across as being disrespectful of the opportunity to have that meeting. If (s)he is expecting to review your complete file, then don't jerk them around with a pre-MCAT meeting, which may lead to a post-MCAT meeting, which may lead to a right-before-I-hit-send-on-my-AMCAS meeting. Be efficient with what you want to present and what feedback you'd like to get.
Furthermore, it's only December, and you don't have to submit your AMCAS until June. So, you have plenty of time to schedule this foray.
If I were you, I would wait. The MCAT is such an important part of your file that this Dean is likely to say, "Well, it's going to depend on your MCAT score." So, in the spirit of not pissing their time away, I would just wait. Make it count.
(Source: I've held audience with a couple of Deans and a Trustee, in my time.)