My $0.02 -
* Have them watch YouTube videos of other robots doing this year's challenge and see if they can emulate any clever ideas they see. They can learn a lot that way.
* Spend some time teaching them about proportional control. It's good for all sorts of stuff in FLL.
* Challenge them to redesign their strategy to use different sensors. If they used color sensors and the gyro, challenge them to try to build something that uses the ultrasonic sensor and touch sensors.
* Keep an eye out on this list - you'll often times see requests for teams to come exhibit their robots at various events in the area