Spin this wheel 5 times to decide which five units the player will take to a level, and if the configuration is impossible for whatever reason (e.g. Blanket, Cat Tree, Freezer, Cereal Bowl, and Catnip), refresh and try again.
Then pick a level using this random selector. 1 - 20 correspond to Inuit Land levels 1 - 20, and 21 - 45 correspond to Beach Land levels 1 - 25, just subtract 20, and 46 - 53 correspond to Area 51 levels. If the level is unsuitable for random units, then randomize again. The game-master should accomadate for the player if there is no unit picked to deal with the starting zombies; make the zombies spawn later.