This site is a good site for your kids to learn more about the environment and science. It encourages them to draw out what is in the backyard--from trees to animals to other things that they would discover there. The site isn't limited to your actual backyard but can also be used for parks and other places, or just let your imagination go and make something up.
To get some ideas, click on "explore backyards" and "explore discoveries". That's where you'll find the yards of other users of the page and their discoveries.
To start after you've set up an account--you don't need an e-mail address to do that--click "make a background" or ".....discovery" from your page. For a backyard, click and drag an icon into place and then size it up. For discoveries, either download a picture or draw it yourself.