If you buy say sausage rolls and pork pies on a Thursday and keep in the fridge overnight, then travel Friday for 5-6 hours with them in a cool box with ice blocks, then put them back in the fridge Friday overnight, then serve up for buffet on the Saturday, is this too many temperature changes over 2 days?
As long as you have enough ice to keep them cold the whole time, that's the same as just putting them in your fridge for a couple days: they'll be chilled, stay chilled, then get served, whether warmed or just naturally brought toward room temperature.
So be sure you have enough ice, and as usual be sure not to let them sit out forever to serve, and you'll be fine.
When packing your cooler, put the ice above the products that need to be kept cold.
If you can find it, "dry ice" is better than conventional ice, as it doesn't melt into water. Dry ice also doesn't need to be placed above the item, as the cold doesn't just go down. The gas it releases fills the whole space, chilling the whole cooler.
A 5 inch by 5 inch square, 1 inch thick will typically last for 24 hours. Multiple squares will increase the time that it can keep the product in a "below 41°F" condition.
( For those who cant obtain dry ice. Use 2 garbage bags to use for your normal ice to help ensure your food does not get as wet as it would otherwise. (( food will get a bit if condensation with double bagging the ice reguardless )) ) Added. 4/25/2017. VIA joes' opinion
Use gloves when handling the dry ice as it causes instant freezer burn on bear skin. I recommend a polymer blend glove, leather and cloth sticks to the dry ice. Do not use latex or food service gloves to handle the dry ice as instant freezer burn penetrates the thin layer protection anyways
For your length of trip, normal ice should be plenty, but make sure it's on top of what you're transporting, and for either ice you need to use an appropriate container. It is best to wrap the dry ice so it does not touch bare food that causes freezer burn aswell, i recommend wrapping the dry ice in bubble wrap but leaving 1 5 inch by 1 unch side open facing the middle of the container.
Dry is is the best when transporting food safely because it is waterless, lasts a long time in a sealed enviornment handling needs to be diciplined to remaind unscathed but besides the few extra steps (to protect your self its the way togo). Added. 4 25 2017