To handle the ambush zombies (the zombies who appear from the pool out of nowhere), I use my cob cannons. I fire the cob cannon 7-8 seconds after the last sign appears. You can also use Ice-shrooms and Doom-shrooms, but I prefer to use my cob cannon.
If there's a situation where you don't have any cob cannons available, use cherry bombs.
Ballon Zombies are no threat. Get rid of them with a Blover. I wouldn't recommend Cattails since they can sometimes pop the ballon where the Ballon Zombie can eat my cob cannons and block the shots of the Winter Melons and Gatling Peas.
Dolphin Rider Zombies are no threat at all since the Gloom-shrooms in the pool are placed right to deal with them (they will jump over the Gloom-shrooms and then 4 Gloom-shrooms will attack them at once). When the Dolphin Rider Zombies are swimming, they can't harm anything, and are killed before they reach the Gloom-shrooms without the pumpkins.Miner / Digger Zombies get killed by the Gloom-shroom at the back, and it requires no repairing since they won't be able to reach the pumpkins.
Bungee Zombies sometimes will steal your plants. If you want, use a Ice-shroom on them.
Giga-Gargantuars (or normal Gargantuars) are no threat at the row with Gatling Peas. However at the row with Winter Melons you should use cob cannons on them and let the Gloom-shrooms at the pool finish them.
Pogo Zombies are no problem. They're fast, but will be slowed down by the Winter Melon. While they're going, they're gonna get killed by the Gloom-shrooms in the pool.
Catapult Zombies are no threat since the basketballs bounce off the Umbrella Leaves that protect the plants.
Jack-in-the-box Zombies are quite dangerous since they can explode at the Gloom-shrooms at the pool. Kill them ASAP.
Snorkel Zombies are no problem since they are killed quickly by the Gloom-shrooms at the pool.
Zombonis are no problem. If some get close, cob them.
Dancing Zombies (more specificially Backup Dancer Zombies) are only dangerous on the 2nd and the 5th row since they can eat the 2 cob cannons. I'd cob them.
You won't need to worry for sun since there are 2 Twins. If your sun gets low, though, plant 4 Twins at the back when there's a round without Miners and Catapults.
Ladder Zombies are useful since they ladder your pumpkins, making them invulnerable to zombies, but then again, their speed sometimes gets them bitting my cob cannon. Make sure the Winter Melon slows them down and then cob them.
The plants I bring EVERY round are:Lily Pad, Squash, Cherry Bomb, Pumpkin, Imitator Pumpkin, Kernel-pult, Cob Cannon, Coffee Bean, Fume-shroom, Gloom-shroom.