This scene represents the theme of women being independent. Usually, in movies it is stereotypical for the male to rescue the helpless women, but here Mrs. Incredible takes charge and goes with her kids to save her husband.
This scene of them in their super uniform represents the theme of family. It does this by concluding that family should stick together and not try to hide things and go alone. Instead, they should all work as a team.
This scene represents sadness and not living to your potential. It shows Bob working at his horrible office job when he wants to be a superhero again. He's not living to his full potential for being a superhero. The scene also has him alone in a cubicle to show Bob's sadness and loneliness.