I can't begin to explain the value that I put in someone that is willing to work hard. I hope and pray that each one of us will instill that solid work ethic in each of our children. It seems to be a dying trend in some regions.
So, to me, the question is not, "Should we teach our children the value of hard work?", but rather, "What will your children work hard to get?" What do you want your child's "payoff" to be? We often think of a "payoff" as money, but it can some in so many forms.
If their "payoff" is a strong family then that payoff will come when they spend many hours figuring out family dynamics and how to build stronger relationships. We can help by being a great example of a father, mother, brother, daughter, etc.
If their "payoff" is a good education and strong financial future then their payoff will come when they spend countless hours studying, both books and real-world economics. We can help by providing them the means to learn through books, taking them to the library and learning about real careers.
If their "payoff" is a strong relationship with God then that payoff will come when they spend their time focusing on reading the Bible, praying and working hard to be more like our Savior. We can help by being an example of a true Christian, not telling them how to be a true Christian.
If their "payoff" is philanthropy then that payoff will come when they devote hours upon hours helping others that are in need and truly making a difference for future generations. We can help by being great examples of cheerful givers.
If their "payoff" is purely money, I think we failed to teach them about the true values in life.