I found these one Social Design and feel in love! According to their makers, Wishes in the Sky - these are traditional Chinese flying lanterns made from excellarated biodegradable materials which makes them a green and affordable choice over fireworks for a wedding! They are about $8 a piece and are sold in packs of 10 and for each pack sold, about $4 US is donated to the rainforest Concern project. Each box will save .2 acres of rainforest.

If you have the budget to provide one of these for each of you guests (about $800 for 100 guests, still WAY cheaper then a decent fireworks show) you can make this a group effort for your entire guest list or if you have a more restricted budget, go with one box and have the bride, groom and wedding party each release one instead.