You can reserve up to three FastPass+ per day, and these can be scheduled way in advance. If you're looking to go on all three rides in Toy Story Land without an organic wait time, be sure to reserve all three, then check in with your Magic Bands during your scheduled time. If you're looking to book FastPass+ for other rides or attractions around Hollywood Studios and only have space for one in Toy Story Land, definitely make it Slinky Dog Dash — your kids will want to ride it more than once, most likely, so having a FastPass+ for at least one of the times ensures they'll get to ride.
Image Source: POPSUGAR Photography / Alessia Santoro