Craig T. Nelson is already confirmed to be coming back as Bob. If the kids are older, it's believable that their voices might have changed, so while we'd like to see the original actors back, they're not as crucial. But The Incredibles really wouldn't be the same without Holly Hunter as Helen/Elastigirl. Her lively, distinctive twang gives the character a unique personality, completely believable as a thoroughly competent but slightly overextended housewife and mother. She's great in the comedy scenes and heartbreaking when she thinks Bob is cheating, but she really shines in this clip. Hunter made sure she learned the meaning of every bit of technical jargon that Helen spits out here, and the animators had to rework their storyboards a bit just so they could match her intensity.
T Campbell has written quite a few online comics series and selected work for Marvel, Archie and Tokyopop. His longest-running works are Fans, Penny and Aggie-- and his current project with co-writer Phil Kahn, Guilded Age.