I know you said monorail, but I'm gonna go outside the box and recommend Geyser Point at Disney's Wilderness Lodge. It's a short boat ride away from Magic Kingdom, has some really solid food, and is often overlooked/not-as-well-known about, so it shouldn't be too crowded. We really love how secluded it feels. It's an open-air restaurant. On one side is the Wilderness Lodge, on the other side is Bay Lake. You genuinely feel like you're in upstate New York or the Pacific Northwest (minus the sweltering heat and humidity most days). It's a nice, peaceful, change of pace after fighting the crowds in Magic Kingdom.