Minikit 5
After you drive off the troop transport, bring in a strong character to pull apart the container with the strength handles.
Minikit 6
Before starting the Blaster Battle (or after you finish it), blow up the silver LEGO object off to the right to fill a dive spot with water.
Minikit 7
Backtrack to the mound of sand closest to the point where your characters began in the area. Assemble a Minikit from bricks that appear.