Cut paper trash with online invitations. Have your child design an invitation, then scan and send to a group email; or use a free template at evite.com.

Make it easy to carpool; send email attachments showing bike routes and bus lines. Use compostable paper plates and bowls. Better yet, serve finger foods that don’t require plates.

When they arrive, give each guest a cup with his or her name hand-drawn or painted on it to reuse and take home after the event.

Scout out secondhand and discount stores for inexpensive flatware and cloth napkins; charmingly mismatched, they look great arranged in wicker baskets.

Set up clearly marked bins for compost and recycling. Offer only one very small trash bin with a sign reading “Zero-Waste Event” to inspire young partiers.

Shop in bulk, and avoid foods with extensive packaging—especially plastics.

Skip the streamers, balloons, and plastic party favors. Decorate with potted plants and bowls of fresh fruit, and send guests home with earth-friendly treasures: mini clay pots with seeds for planting, wooden birdhouses to paint, or small framed photos.