I've got a 4 year old and a 6 year old. All valid things you raise here, and they certainly still apply with mine at their current age.

A positive though, that may not apply to everyone, but certainly applied to me: They make you grow up

Suddenly there are other people that really depend upon you. Whilst finding the time to get a startup running is harder, I think the motivation to succeed is stronger than it was when it was just me with few cares in the world.