combined question for you. which type of goldfish are you talking about? the ones you get from pet store, (2) miniture coi type?
either one isn't hard and just about the same. i use to live in ca and drove to colorado river (4-5 hrs) in heat.
1. bag them with 02 shot into bag. ice chest with some blue ice and they did well.
2. 5gl bucket and put fish in with a battery airiator (spl). add ice cubes as you go if hot.
but, if they put in bag and fill with tank of oxygen, they should last for 3-4 hrs if you keep cool. just when you get there, set the whole bag in local water for 20 minutes or so, so they get used to warming up and don't go into shock.
i very seldom lost any on trip. now i live in az and it's hot. just change water and use portable aquarium pump.
gary