That is the age old question....
One thing you have in your favor is first hand 'family' knowledge. You said your Brother-in-Law made the move and is very happy. Seems like he would know many of the questions you are asking.
Youngsville is a nice area, I would classify it as rural. I don't know about their schools so I cannot comment. They are in Franklin County and not Wake. If you want to be closer to more shopping, activities for your children, and a short drive to Youngsville you may want to check out Wake Forest. It is south of Youngsville on Rt 1 South. It would be on your way from Youngsville to mall shopping, or visiting downtown Raleigh or RDU airport.
Quality of life is good but that is a very subjective subject. If your from a larger town in New Jersey nearer to NYC you may think Youngsville is to slow of pace. But as the other poster wrote that is truly up to you.
Here is a website on Wake Forest! Good luck with your decision.
Welcome to the Town of Wake Forest, North Carolina