The best answer to your question will depend a lot on where you're located.
For example in Idaho and Utah large families are fairly common and at least 4 bedrooms would be a plus on resale.
In area like for example, Tennessee where I am, 4 bedrooms might be nice but 3 would work for most families and they might appreciate having a nice living room in addition to a family room.
One thing to keep in mind unless you've built a new garage to replace the one that became a family room; lots of buyers in my area want a garage. In other areas it might not be that big a deal.
Bottom line, as long as what you're offering for sale conforms to the norms for your area and it's priced right plus being in as close to "move in" condition as you can make it, it should sell.