Hey man,
depending on your GPA, a 27 can get you into a DO school. I would submit without inputting the new MCAT date in the system. This will allow you to get the ball rolling ASAP. If you decide to take the MCAT, after you get your score you can input it into the system. The schools will receive the score. If you take it and void it, then it's all good! You don't have to worry about a thing since the schools won't know.