Want a great way to celebrate both?
Plant a tree or 10!
The Arbor Day Foundation is a nonprofit organization who want to inspire people to plant, nurture, and celebrate trees. To this end when you join for $10 you get 10 free trees. If you have no room for trees in your yard then they will Plant 10 trees in a national park in your name. Their wonderful site is full of information about different kinds of trees. They also make it easy to find the perfect tree for you. Whether you want a pine, fruit, or flowering tree (or any other type) just put in the type of tree and then your zip code and they will give you a list of the trees that will work best in your zone. They also have a youth educations section so you can share the love of trees with your kids. Visit http://www.arborday.org/index.cfm or just click the tree for a quick link.
Come back later for some more Earth Day Ideas.