This is the hardest level in the game. Make sure that when you get the first balloon you jump into the bottom of it and not the top. This will give you a significant speed boost over falling onto the top of it.
Be sure to take your time as you approach the football players. The balls can do a lot of damage to your health.
Time it just right and it should be easy.
Another way of finished the level is using a blue Yoshi and a cape.
Walkthrough
Jump onto and past the Chuck ahead. Go past the next pipe (watch out for the piranha) and run and jump into the Dragon Coin and over the chuck. Go over the yellow pipes and activate the P-Switch. Now quickly drop down and left onto the springboard, and hit the ? block and collect the P-Balloon that comes from it. Float and get the Dragon Coin that's under the block, and go up and collect the Dragon Coin above the Chuck on the block. Hit the ? block just to the right and renew your inflatingness with the P-Balloon. Head through the flying Koopas and collect the Dragon Coin that are between the volcano flowers when the coast is clear. Go onward, past the yellow pipe and under the Chuck so you can get another P-Balloon. Now watch out for footballs from the above Chuck when getting it, cos unless you are prepared, one WILL hit you. I recommend that you wait until one has been throw and gone, then hit the block and get the P-Balloon. Hit the block that the Chuck above is resting on (for safety sake, and for revenge) and go under the next to volcano flowers, and onto the exit. Save.