Humans are hardwired to recognize and remember faces. These are heavily personified characters that drastically vary stylistically. What symbol do you use for a country? A flag? German, French, and Italian flags are all very similar. It's not that you should treat your audience like they are idiots, but good design should mean anyone can use them without prior knowledge. "Oh we parked at the raccoon thing, the robot, the turtle," etc, is possible without any prior knowledge of the individual IPs. You want to give people as many things to grab onto to remember something like this.
Did the original scheme have any purpose? Colors do the trick. Sure, could set the tone for what you're about to expect in the park, but function over form in this situation without hesitation.