I'm trying to teach my kids to start saving as soon as possible. I didn't start a 401k until I was 28. I dumped 17% into it for a short time, until I got married and decided I couldn't afford that anymore. I always put in enough to get the maximum company match, but wish I had started earlier and put more in longer.
I'm pretty sure I could talk until I was blue in the face, and not force my kids to learn from my mistakes. Sometimes people just have to learn on their own. I just hope it doesn't take them as long as it took me.
I'm not sure how old your kids are, but my folks did the following with me:
1) Told me that I had to save 50% of my allowance, and then my jobs in my early teen years.
2) They would help me save when I was very young (5 - 10) and when we would go to the bank, they would match whatever I put in.
3) Get them in the habit early. Really early.