it will be fine for that short amount of time. My only tips - just keep the cooler out of direct sunlight. If the cooler won't fit in the trunk and will be in direct light - just put a big blanket over it for extra insulation. (and yes, tons of ice!

)
We travel to Ontario (6 hrs 1way) and I haven't lost any frozen foods yet and that's in the back of the truck in full light the whole time.