When I go away on a boys trip we run two big eskies, one food and one drinks.
The food esky gets bagged ice zipped into those 8 kg dog food bags with the zip lock thing on top (Those bags are obviously washed out before use). They dont leak at all when you stand them up. Ice lasts for ages and esky is kept cold. When they do start to melt you can just pour off the water into the drinks fridge
Drinks fridge just cops bags of ice in over the drinks and turns into a slurry.
Shade and wet towels do make a big difference.