We always drive (nice being retired), but still buy a lot of food before we leave and take it with us. Same reasons: Have the food right with you immediately so no necesary side trip to a grocery first thing, familiar with local brands, cheaper (milk = $1.89/gallon), already have the local store's discount card, etc. DW will also fill small containers for those things you only need a little of (salt, butter, cooking oil, etc).
We'll take a cooler with cold items (milk, butter), and lots of ice, several packs of pop (typically $2.50/12 pack) and so on. Then a couple of boxes of canned food, bread and such.
Just two of us so plenty of room in the car including the trunk and the back seat. We'll use a smaller second cooler for cold drinks to use on the trip, and a small bag with snacks.
We make a one-night stop enroute, a little over half-way there, will eat dinner out somewhere that night, have the hotel's continental breakfast in the morning, and then finish the drive, arriving at WDW about check-in time, and not having to wait for the room.
Works great for us.