One of the great challenges I've noticed with trying to live a reasonably environmentally conscious life is teaching my children to do the same. Young children have very little sense of the future; for example, my daughter intends to be Rapunzel when she grows up. However, they do possess a decided desire to please.
Things don't always turn out the way they intend, but children generally do mean well. And this means you can teach them. Start out by talking about why you make the decisions you do in terms of helping the environment. Even a preschooler can begin to learn what gets recycled, thrown in the compost or in the trash. A garden is a great way for kids to learn to care for plants, as well as a great way to get them interested in eating their vegetables.
Start them out with organic techniques so that they really learn them and because it's much safer for them than using chemicals. Older kids can help you make more environmentally friendly household cleaning supplies if that's one of the things you do. Measuring quantities and mixing them together is a bit of math practice and a way to teach them that harsh chemicals aren't the only way to clean. Teach your kids about energy conservation.
You can talk about the amount of power the various kinds of light bulbs use and have them help you make a good selection. You can make any child old enough to reach the light switch be responsible for keeping extra lights off. Have them help you to conserve water too. They can help you replace plants that need a lot of water with ones more suited to your area, for example. Show your kids ways to reuse all that wasteful packaging material found in children's toys and electronics.
So much of that doesn't recycle easily in most areas, but you might be able to use some of it at home. Styrofoam packaging in large pieces combined with golf tees and a pounding implement makes for loads of fun for younger kids. Of course you'll have to supervise with smaller kids, but those dratted wires that hold just about every toy in its box these days can be added to the craft supplies.
Also talk to them about using only what they need. This is a really tough one for kids these days, as they are likely to want all the stuff their friends have. As a parent it's up to you to help your children control their more acquisitive urges and to enjoy what they have. Children don't always take naturally to the sacrifices required to live a greener lifestyle, but it's a great time for them to learn the skills.
Have a little fun with it and let your children explore their options as they help you help the planet.
Stephanie Foster runs http://www.greensahm.com/ as she tries to figure out how to live a more environmentally friendly life. With two kids and a husband she finds plenty of challenge in this.