Make use of natural and reusable, recyclable materials like cloth table covers instead of plastic, pieces of cloth instead of paper napkins.
For decorations, you can create a centre masterpiece with all your recycled material. Start collecting all your cardboard cereal boxes, egg containers, any yoghurt tubs etc and spend the time with your kids to make up something. Use any durable items as your containers for the party food.
You can avoid using paper invitations and invite people via email or sms, or use recycled paper should you wish to send hand-out invitations.
Party Favours could be: A green shopping bag or goodie bags made out of used paper or even cloth type bags. Fill it with a globe of the earth and seedling packets. Use recycled jars to fill with sweets. A poster on recycling. Wooden toys.