Besides donating used toys to charity to make room for new ones, teach your children about giving by buying a new toy for a neighborhood charity program like Toys for Tots.
This is really important! I am now 45 years old. When I was six, my folks asked my sister and I if we would give something that Santa had brought us to a child who was unfortunate and needy. I did and I have been giving ever since, some years to the Angel Tree, some years to nursing homes, some years to my church's Christmas program. I have taught my own son, who is 19 now, to remember those less fortunate, too.