A subject near and dear to my heart as our first child approaches her first summer with my 911
According to the MTO, kids under 13 are safest in the back seat. Are you sure she doesn't fit? I've sat back there before for a short highway trip. It wasn't comfortable, but I was ok. I'm 5'7, 190 lbs.
Here's the MTO site on kids in cars: (scroll to the bottom for older kids)
http://www.mto.gov.on.ca/english/safety/carseat/choose.htm