New Super Mario Bros. Wii 5-4 QSC

I got the 2nd Star Coin by using the POW block near where the 2nd Piranha plant falls from the sky. The Star Coin will fall on top of the raft if you don't use the POW block too early or too late. I got the 3rd Star Coin by having a Bob-omb blow up the gray blocks underneath the pipe at the end and falling onto the Star Coin when the raft is underneath it. I jumped back up, went through the pipe and reached the goal.