This cute garden will really help you "grow" your kids' good manners.
Print and laminate them. Then put then in a flower pot.
When I worked this with my students, I introduced them one by one. We worked on it for a week, and then the next one came.
Every time they did not use this "friendly words", I stopped the class for just a few minutes, and talk about how import an they are and then we water our garden with a nice reflection.