When we were on the DDP, we often used snack credits or the previous night's dessert (doggie bagged) for breakfast... ah yes, I had many a slice of cheesecake for breakfast. Hey, it's got protein!
When we pay for breakfast in a food court OOP, it would typically cost about $5-7 for an adult plate, though some places have a bounty platter for $8 and change that could easily feed two people.
We also found that an adult order of pancakes would be cheaper than two kid's meals... but if you need kid's meals, they're about $4-4.50 each and include a drink. (The kid's often preferred the muffins though, for about $2.50 each.)
If you're there for a week, it makes sense to get the mugs for unlimited drinks, so that's $13 as a one-time charge per person... load up on coffee, hot chocolate, soda, whatever... unlimited refills in your resort for your whole trip.
So, roughly, I'd say the previous estimate of $22 for each breakfast in the food court for 2 adults / 2 kids is pretty accurate. A little more if the kids are bigger eaters, less if you share stuff around...