Coping with Invasive In-laws

Approaching your in-laws
Once you hammer out your roles, you'll have to tackle your in-laws separately. For instance, if it's your parents who are interfering, you'll be the one who has to confront them and vice versa. You'll need to tell them, respectfully, that you and your partner have decided to raise your child in such and such a way. While you both appreciate their opinions and are very grateful that they're willing to help out, you and your partner will be parenting the way the two of you have agreed.
Yes, your parents did a wonderful job of raising you, but times have changed. Be sure to tell them what wonderful grandparents they already are and how, as grandparents, they get to have all the fun of parenting with a lot less of the dirty work. If nothing else is working, you may have to take it up a notch or two by telling your parents that if they can't go along with the parenting program as you've outlined it and respect the two of you as parents, they simply won't be able to spend as much time with their grandchild as they'd like to. Hopefully it won't come to that.