Alyson Hannigan and her daughters Satyana, 4, and Keeva, 13 months, were dad Alexis Denisof's biggest cheerleaders as he participated in the Course of the Force relay race at George Lucas's Skywalker Ranch in Marin, Calif., on Tuesday.
Denisof, who was dressed in a self-made C-3P0 costume, "walked rigidly" (just like C-3P0!) in the last leg of the race.
"When Alexis rounded the corner, Alyson grabbed the kids and said 'Let's go watch daddy!'" an onlooker tells PEOPLE. "They cheered him on as he finished the relay with the lightsaber."
In true Star Wars fashion, the actor spoke in a C-3P0 voice to R2-D2 at the finish line while his little ones met Darth Vader and Boba Fett.
"They were such a happy, easy-going family," adds the source.
Course of the Force benefits the Make-A-Wish Foundation.
– Melody Chiu