For my son, I began teaching him before he turned 5. We started with Step Stone, which is the book before Step 1. He didn't show much interest, so we just continued on and off. We also began to play the whole game, but he rarely finished any.
One day I started with a book, which was used when my daughter was young. We worked on the one move checkmate problems, and he liked them. We also played a game, and he lost. He lost interest right away. But the next day, we continued.
I soon realized that the field was not leveled when we played games, so I took out my queen. I gave him hints here and there. When I spot a checkmate, I would switch with him, and let him execute the checkmate. He would be very happy to do that, and didn't care that the previous moves were actually his. Once in a while I would checkmate him, and he would cry. The first time he cried was true sadness. But I hope one day he would stop crying.
Nowadays, we play one game every night, and work on 5 problems. It becomes a habit.
No speech is required to motivate your kids. Playing with him/her everyday is the key. Even if you send your child to me to learn chess, I still wish you could play with him/her everyday. Once a week is definitely not enough. It's everyday's job.
If you need one move checkmate problems, you can check out our book on the right.