Larry David and HBO originally envisioned this as a one-time project, but it eventually became Larry et son nombril (2000). While that series also has ad-libbed dialogue and (during the first 6 seasons) a similar visual style, it's not a mockumentary (the characters don't acknowledge the cameras) and Larry & Cheryl David don't have kids.
This episode can be found in the first season disc set on the second DVD's bonus section.