What time do you plan to eat?
Disney does not really do “brunch” anywhere.
They have breakfast buffets and in a few places, they have lunch buffets.
The only “real” brunch meal is served at House of Blues and perhaps at one of the DTD resorts.
My only workaround has been to get the very last reservation for breakfast at CP, show up a couple minutes late (say 10:30) and then dawdle over your meal so that you’re still eating at 11:20 when the change over to lunch has occurred.
If it’s Easter Sunday, there is a slight chance that Dolphin or Swan could be doing a true brunch.