Try to ride Slinky Dog Dash first thing in the morning.
Even if you have a FastPass+, try to head to Slinky Dog Dash first thing when the park opens. Like I said, your kids will probably want to ride this fun coaster more than once (I can basically guarantee it), but the lines are going to get extremely long superquickly.
Pro tip: for adventurous kiddos, try to ask to sit in one of the last two rows, as the coaster feels much faster back there, and you can feel the little drops more. For younger kids who don't live for speed and toddlers who are tall enough, grab the front rows.