Thats a good question.
My guess would be everyone has to do it for the simple reason they give you a family style salad and the number of flatbreads you get is based on the number of people in your party...1 flatbread for every 4 people. The kids still do get to order off the kids menu and they get a dessert too.
Also, if I remember correctly the voucher for admission states the number of people. So if you were able to only do it for 2 at dinner, that would be stated on your pass.
You can always ask at the restaurant though. Good luck!