The Q & C's may not be used for family size meals anywhere. They used to be more lax on this just because the vouchers weren't widely used and most employees weren't sure about the rules. Now that the vouchers are more common, they will not let you do this. You may not purchase a full size pizza either. They will let you order the individual serving pizza though. You can still get more than enough food using the vouchers the way they were intended to be used though.
Personally, I order 2 for my family of 3 because my DH will need for for himself- he is a growing boy, um, I mean man! My DD-13 and I share with no problem at all. My family has been using the vouchers for the last couple of years (we go to WDW 4 times a year) and will never go without them again!