My toddler (2 1/2) is not so much picky as erratic, and I decided I was on vacation and I was not going to fight with him over his eating habits while we were in WDW. Besides, it was 90 degrees+ while we were there, and I figured he would not starve in a week, but he absolutely could not dehydrate (luckily, he loves water).
That said, the buffets we went to worked out, and since he was under 3 we did not have to pay for him. At the Garden Grill at EPCOT, they served him chicken strips, mac 'n' cheese and french fries. He chowed down on the mac 'n' cheese and the fries, but he did not care for the chicken strips, either there or anywhere else in WDW that he got them, although he did eat the chicken nuggets from the ABC Commisary in MGM, and I noticed that there were McDonald's stands in the parks that served chicken mcnuggets. Plus, he got to meet Mickey, Pluto, Chip and Dale.
We also took him to Chef Mickey's for breakfast. They had so much to choose from, he was fine. But, he was so busy with his Mickey pancake, he didn't want to deal with the characters.
At Ohana's, all he ate was bread and rice, but he did like my virgin pina colada. Oh, and he loved the pineapple dipped in caramel they brought for dessert.
Right before we left for WDW, he got on a peanut butter and jelly kick. Aunt Polly's on Tom Sawyer Island had pb&j bag lunches (I would take it with you, there was so much bird poop on the patio it was too disgusting to eat there). The Concourse Steakhouse and the Rose and Crown in Epcot also had pb&j.
We got a couple of hot dogs into him, and anytime french fries were offered he ate happily. He also chowed down on pizza.
The biggest problem with my approach, sometimes we wasted alot of food. But, we came back from vacation rested and hydrated.
Have fun!