Cherry Bombs should be used on zombies like Conehead Zombies and the final wave, since the game attempts to overwhelm the player. However, the level is very short and will conflict with Cherry Bomb's very slow recharge speed. This means that the player can only use a few Cherry Bombs through the span of the level, and should only be used when tough situations arise. This level, however, is beatable without Cherry Bomb.
Lawn Mowers will help if the player cannot beat the level.
Strategies
Plant two or three columns of Sunflowers closest to the house, then three Peashooters in front. Use Cherry Bombs if you are struggling.
Gallery
Plants vs. Zombies Wiki has a gallery for Level 1-3.