I suggest for the tried-and-true method of screwing up more often yourself, or making it obvious to him when you've made a mistake, and showing your son how you handle it. If I drop a jar of pasta sauce and it breaks, I capitalize on it as an opportunity to teach my son, "Oops, mommy made a mistake. She accidentally dropped this sauce. No big deal, we've just got to clean it up." Likewise, in my classroom, if I accidentally misspell a word on the boear, I'm happy for the chance to remind my second graders that "nobody's perfect- see, even I make mistakes!" And of course, it will be especially important for your husband to learn to do the same. He is the one, it seems, who is doing most of the modeling or perfectionistic behavior. You won't be able to change it by yourself if he continues to be that way in front of your son. This may be a good opportunity for him to learn to "loosen up," and it may wind up helping him feel more relaxed, too!