Tigerbear,
It depends on what the adults like to eat. And what kind of service you want.
At the Plaza you typically get your choice of omlettes (made to order for you), home fries, bacon, ham, sausage, gravy/biscuits, scrambled eggs, fruit (often frozen), small bagels/cream cheese, cheese crepes, waffles, cereal and assorted beverages. It is completely serve yourself. To me, this is geared more toward the kids and has an I-Hop feel to it (the food, that is.) They charge $20.95, I believe. You don't need to tip anyone here.
At Storyteller's Cafe you typically get your choice of fruit (typically fresh), bagels/lox, the most delicious french toast anywhere, eggs benedict, a Mexican dish, home fries, ham, sausage (large), fresh danish & pastries, omelettes made to order. To me, this is more geared toward adults. It's the least expensive character breakfast that I know of at $18.95 per head. The servers bring you your drinks here. You tip the servers for bringing you your beverages. You can also order off of their menu. To me, this feels like the type of high quality food you can expect to get in California's most popular breakfast spots. High quality and a good assortment of healthful choices. It's also the most beautiful spot for breakfast, in my opinion.
At Goofy's kitchen you basically get all of the above for, I believe, $21.95. The servers bring you your beverages here and -- yes -- tipping is probably more expected than not.
If you are a premium annual passholder, don't forget to present your pass for a 10% discount at each of these places.
I think everyone covered the character availability at each pretty well. You find the most characters at Goofy's Kitchen, the least at Storyteller's. You find Pooh characters at the Plaza.
Hope this helps!