Sometimes your child may simply be too short to ride (especially on the high end rollercoasters). If you find yourself wanting to ride an attraction, and your child unable, you might consider the "Rider Swap" program offered by Disney.
This complimentary service allows adults to switch off riding an attraction without doubling the wait time. It's perfect for those rides where you don't have a Fastpass. Here's how it works:
Be sure to ask Cast Members about the "Rider Swap" program for your favorite adult attractions!