Heat transfer: meatballs and ice

I have a heat transfer question. It's a mother/daughter argument ready to happen and I need backup.

My mom is transporting 10 pounds of frozen Swedish meatballs (in 4 bags) from Minneapolis to Bismarck by car tomorrow. That's a six-hour trip. The objective is to keep them frozen. She's purchased a small cooler. The cooler is exactly the right size for the meatballs, with no space left over for ice. The question we face is whether the meatballs will fare better if she fills the single cooler with meatballs and no ice, or if she buys a second cooler and fills the two coolers half with meatballs and half with bags of ice.

I'm thinking the heat transfer coefficient of the meatballs is lower than that of ice (i.e. that meatballs thaw more slowly than ice cubes melt, given equal surface area in identical environmental temp), and further that the meatballs have less surface area that the ice cubes and therefore she'd be better off filling one cooler with frozen meatballs. I KNOW she's not going to believe that such a thing could possibly be true.

I could well be wrong about the comparative heat transfer coefficients of meatballs/ice (opinions, please), but if I'm right about that, then I'm right about the cooler conclusion, am I not?

I guess there's one other factor to consider. The meatballs, being bigger than the ice cubes leave greater air space between/amongst them than a bag of small ice cubes would, and that would result in faster heat transfer/thawing. That favors the two-cooler plan.