Use the Rider Switch Pass or Baby Swap
One of the least publicized services Disney offers is the Rider Switch Pass (often called the Baby Swap), and for parents with young kids, it means everyone can have fun in the park.
Here's how it works: if you have a child that is too small to go on a ride, you don't have to wait on line twice if both parents want a go at it. Simply all wait in line together the first time (and if you have a FastPass for the ride, the whole process is even faster). When you get to the front of the line, ask for a Rider Switch Pass. The first parent can go on the ride alone or with a child who is big enough to ride it. When they are done, the second parent (and the big-enough child, if he wants) goes straight to the FastPass line and gets to ride it again, meaning no hour-long waits!
And here's a lil bonus tip — you don't have to use the SwitchPass right away. If you obtain it in the morning, but want to wait to go a second round in the afternoon, you can!