I think the parks are way more health conscious than they use to be, you can find rotisserie chicken, salmon, hummus, fruits and veggies all around the world. Even if you splurge and get a burger, you can typically add veggies, or apples slices as the side inside of fries. And as other suggested, just share, most of the portions are more than enough for just one, and this is a great way to try lots of great foods around the world.
I don't recall seeing any calorie posting though, sorry.