OP you're over thinking it. With good coolers what you're asking for is easy - my big 6 day Coleman still had ice in it after 8 days hunting in 0-10c a month ago. Just pack the coolers tight, and don't open them until you get to your destination.
If you can't fill the cooler with frozen meat, add ice in the form of frozen plastic bottles. I prefer 500ml water bottles or 2l juice bottles, the ones that are somewhat rectangular such as cranberry juice.