A DEFENSE FOR 11-13 GIRLS

I have a 5'10" twelve year old, a little clumsy, two girls who are 11 & 13 and are about 5'4, heavy(around 155) and have never played before. Everyone else is smaller and obviously quicker. I planned on running a high 1-4 to keep the movement down to a minimum for the big girls except for screening. So, my problem is defense. I thought about a 2-3 zone depending on the team we play. I have a quality utility player who is 5'2" and about 110. She can play point if I need, will be primarily a wing, but can also be physical in the post. I have 2 other girls her size, but have never played before. Is there a defense that can utilize my quick players for man-man, but utilize the big girls for zone? I would just like some specifics on such a defense. I am so busy teaching fundamentals right now, my head is going to explode! My first game is the 11th and we only have a total of 6 practices before then. HELP!!!