Yes we have the Thule Pro-Ride on the roof. We've got 2, but I've seen a Getz with 3 so I guess you can fit as many as you like
Where is your child seat? While we only had one child (over the left) we could still pop down the single seat on the right and put a bike upside down without the front wheel through the gap, but now we've got 2 seats the space is at a premium!
Have you looked at the Thule rack that goes on the hatch-back? I know it says it's suitable for the Honda Jazz so it might be worth a look. We're thinking of one in the future, as we might need to roof racks to transport luggage for holidays.
Still a cyclist, albeit one who never rides any more....