I'm not gonna argue with your choices in life, and I might make the same ones if I had a family that goes through 12 gallons of milk a week, but it's not impossible to pull that off with fewer cars and a smaller garage.
Scenario 1: dense urban living, somehow you can afford an apartment big enough for everyone. No car, just good transit (e.g. Hong Kong, Singapore, Tokyo). Grocery store is <3 minutes walk from the front door of your apartment, so you get 2 gallons every day. With a family that big, you're probably picking several items up, but you'd use a trolley (like this: https://www.argos.co.uk/product/8653909?clickPR=plp:4:6 or bigger: https://www.kmart.co.nz/product/foldable-beach-trolley-42365...)
Scenario 2: big terraced/row/town-house (shared walls on two sides), has a 1-2 car garage. Suburban-ish living, car dependent, but definitely not rural or outskirts of a city. You own a van, which you'd need anyway if your family is big enough to need 12 gallons of milk a week, and then you have your big chest freezer in the garage and you go once a week to the grocery store and get 12 gallons of milk.
Scenario 1: dense urban living, somehow you can afford an apartment big enough for everyone. No car, just good transit (e.g. Hong Kong, Singapore, Tokyo). Grocery store is <3 minutes walk from the front door of your apartment, so you get 2 gallons every day. With a family that big, you're probably picking several items up, but you'd use a trolley (like this: https://www.argos.co.uk/product/8653909?clickPR=plp:4:6 or bigger: https://www.kmart.co.nz/product/foldable-beach-trolley-42365...)
Scenario 2: big terraced/row/town-house (shared walls on two sides), has a 1-2 car garage. Suburban-ish living, car dependent, but definitely not rural or outskirts of a city. You own a van, which you'd need anyway if your family is big enough to need 12 gallons of milk a week, and then you have your big chest freezer in the garage and you go once a week to the grocery store and get 12 gallons of milk.