YES program allows for the purchase of steeply discounted park tickets if you sign your child(ren) up for a Disney-run educational program. They're limited to a certain number of discounted tickets per participating child and it appears they have one person over the limit.
The problem with combining YES with free dining is that free dining requires a purchase of a vacation package including at least 2 day park tickets for ALL persons registered in the room. Which means that even though they get discounted park tickets through YES, they are required to purchase MORE tickets for their entire party in order to get the free dining. This means they will probably pretty much negate the discount they get from the free dining.
One solution is to book the free dining, book the 2 day tickets for everyone, then save the 2 day tickets for a future trip. WDW tickets do not expire until after they are first used. As for the adult who needs tickets, their 2 day ticket can be upgraded to a 7 day ticket once they arrive and check in and receive the ticket.
The only thing I want to mention from the previous post is that free dining does not require 5 nights. Free dining is a 3 night minimum and a 14 night maximum. And you can add any length of ticket you want to a free dining package, as long as they are for at least 2 days.