I have traveled many times with a cooler (legit medical dietary requirements, need to meal plan, preference, etc.) and in my experience, proper packing is the key.
Freeze everything as cold as you can get it, for as long as you can freeze it. Don't wait until the night before to package and freeze items, do it a week in advance.
Vac- packing makes the meat/meals very dense, eliminating air pockets. Having a densely packed cooler is key to keeping it frozen.
Use a high quality cooler. I like Polar Bear brand. Using a layer of techiice ice around the food gives another layer of protection. More than once, we did 36 hours with everything still frozen solid.
As long as the meat maintains a safe temp, a little thawing is fine.
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