While waiting for Grave Buster to recharge, do what you need to do first: plant some Sunflowers at the first row to save enough suns for Wall-nut.
When the Grave Buster is ready, plant it in front of the third endangered Sunflower (the one in the middle lane). It'll open the way for you to plant the Wall-nut. Then continue planting Wall-nuts in front of the endangered Sunflowers and Sunflowers at the first row. If a Wall-nut has been eaten, replace it by an another Wall-nut.
After defending the zombies, plan your attack. Plant the Cabbage-pults between the Sunflowers to attack the zombies.
Tomb Raiser Zombies can be dangerous for keeping spaces for planting, so plant Grave Busters on the graves to clear them if needed. In case of emergency, if you don't have any Plant Food, freeze zombies with Iceberg Lettuce to delay them. If the Iceberg Lettuce is still recharging, try to delay the zombies by feeding them with the other cheap plants. If you have Plant Food, feed it to Iceberg Lettuce or Wall-nut (for defending the endangered plants) or into Cabbage-pult (to deal huge damage to all of the zombies).