Pre-Frozen foods help keep a cooler cool. You can keep bags of ice in the bags to keep it 'clean' for use in drinks and such.
We take a few special items with us, the rest we restock during the trip. About every 3rd day, which we combine with a lunch or dinner out.
A few pre-frozen drinks (water, gatorade, etc) also help and are still quite cold and refreshing when thawed.
Aside from that, we keep an outdoor cooler tucked under the trailer for items not temperature sensitive and reserve the indoor freezer/fridge for more sensitive items.