Having a cape, feather and Yoshi make any level easier and this is no different. If you do not have a cape use the 2 turtle shells to kill the football-throwing Chucks. Use another shell on the third Chuck. You can also spin the cape to kill the Chucks. Using the cape, float up to the ledge before the checkpoint and get the checkpoint. Go through the green tunnel.
Throw turtle shell down hill ahead of you to kill all enemies, if you keep up with it, you can get an extra life. Fall down the slopes but beware of regenerated turtles. Also remember to jump over the black clams of death where the second row of coins are, when falling to the right. Go through the green tunnel.
Having a cape here is also extremely helpful. This screen is difficult, speed is vital. Navigate up the "stairs" and over the red spiny turtle. As soon as you touch the first yellow ledge it will start to sink, jump to safety (this one is easy). Again navigate the red spiny turtles. Then there are a series of flat yellow ledges. When you touch the first one, they all start sinking, so you must sprint across them very quickly. Carefully jump over or spin cape the Chucks, if you do not have a feather in reserve, get the mushroom from the box, and proceed to the next series of slanted yellow ledges. Again, have a cape. Sprint across these as well and jump and float to safety near the end. The arrow sign is in sight. Go through the green tunnel, and the Exit is on the other side.
The green tunnel after Chocolate Secret brings you to the surface, bypassing Chocolate Islands 3&4 and next to Castle 7.