I will almost always wear light-colored dress slacks, or perhaps khaki-colored chinos with a polo shirt or, in cooler weather, an Oxford-style shirt. My wife will generally wear a dressier sundress, or perhaps capri pants with a dressy top. Our children love to dress up, so DD6 is almost guaranteed to be in a dress and DS2 will generally be in chinos with a polo shirt. We do tend to be amongst the dressier families, but it's how I feel most comfortable. Clearly WDW wants their guests to feel comfortable, so as long as you adhere to the basic guidelines set forth, you'll be fine and there will almost certainly be people dressed like you, as well as people more and less dressy.