The stated occupancies are 4/4/8/12. MS will allow ONE under 3 not to count and have been allowing 5 TOTAL regardless lately in a 1 BR. A GV plus a studio might be your best option.
How do your families break up? It might be better for you to book a 2BR and then a couple of studios. Give non-charging keys to the 2BR to the studio familes so they can use the laundry and hang out. If you get up to 3 extra studios, you may want to consider 2 2 BRs. Even so, you'll have people sleeping on the couch.