There are many tricks to finding collectables. Here are a few that might help you

1. Once you have level 3 explore they show up on map view BUT you cannot sit on map view and have them show up because they wont. Just click map once in awhile till you see one.
2. If you dont have the above just pan around till you see one. Once you do
3. Click map, look at the kid friendly spots. The lumber pile...middle of the beach...coconut trees and the blue flower. Click the spot to go right to the kid. Grab the kid
4. Hit the number on the keypad to where the collectable is and it zooms you right to that spot then just drop the kid.

All in all once a collectable is spotted it only takes about 6 seconds to grab a kid from the map and hit 8 to go grab the beetle, or whatever collectable happens to pop up. And they run faster than adults so they are easy to spot on map view