Do you think that older parents should foster or adopt children?

My wife was so distraught when we went to our youngest child's graduation, at his elementary school. She said it was the last time we would ever deal with an elementary school. The children are growing up so fast and one day will be gone. My wife and I will be in our late 50s. Is it fair to small children to be cared by foster or adopted parents, that old? What is YOUR sage advice???