That said, I do try to make the best choices possible when we "have" to go to fast food restaurants. Most kids are going to want the kids meal - the toy just sucks them right in (even if they only play with it for about 15 seconds).
Burger King actually has a pretty informative Web site that allows you to build your meal and see the nutritional value of it. From what I gather, the best kids meal to get would be mac & cheese, apple fries (I ask for it without the caramel dipping sauce), and low-fat milk - a total of 230 calories. Plan ahead of time, and you can make the best choices, even in a not-so-good situation.