At most regular restaurants, you can get a way with sharing as long as it's not a buffet or all you can eat meal BUT since this is a Fantasmic Package meal, everyone must participate.
I ate there this past Oct/Nov and my 6 year old wasn't hungry and is a very picky eater and they would not let her share with her sister. The charged us which I totally understand. I wasn't thinking when I told the waitress she wanted nothing. She said but I'll have to charge you anyway so we got her some food which she didn't eat but it was my choice to eat there so I wasn't going to complain.
Regarding the voucher, you get ONE for your group and one of you turns it in when you arrive at the special entrance.