It depends on where you are going to use the VKL's and if they change their policies before you go.
We ate at AK RFC. 1 adult, 1 teen, 2 boys. I had 1 adult and 2 kids vouchers and we were able to order off of the adult menu for all. The waiter encouraged us to get the max out of the voucher. We mainly just ate the appetizers and a bit of the entree. Took everything else back to the hotel. It was a ton of food. You would have plenty with 1 ad and 1 child there.
I don't know about the other restaurants tho