travelling with cooked chickens
This scenario is on the borderline, if the travel time were the only factor.   Generally, you don't want to hold foods in the danger zone (40 - 140 F / 8 = 4 - 60 C) more than about 2 hours.  However, you have indicated you want to cook the chickens earlier, so that adds on to the time they would not be at a proper temperature if you tried to keep them hot.

The safest method, then, is to chill them properly, and transport them in a cooler packed with ice.  Putting the chickens into zip-type bags will keep them from getting water logged.

See also:
How do I know if food left at room temperature is still safe to eat?