My father said there were two kinds of people in the world: givers and takers. The takers may eat better, but the givers sleep better.
It is up to you and your example to show your children whether it is best to be a giver or taker. I believe the difference is in your attitude: whether we are grateful for what we have and choose to give freely of our substance to others or we are petty and jealous and keep every penny for ourselves.
We have to teach her children that it sometimes seems that the takers get the short-term, more desirable reward, but that givers obtain the actual better reward over time.
If your church has a system of tithing or donation, explain this to your children and why you do it. Show them the service or charity that you do. You make it a part of their life early on, and it is more likely that they will grow up to givers as well.