S.B.
I think it's great you are thinking this way!
The first thing that comes to mind is ask that the gifts be labeled but unwrapped, that would save a lot of waste. We went to adult party this weekend that did this, they just had the gifts displayed on a table and people could walk by and look, we didn't have to all sit around and ohh and ahh while presents were unwrapped so that was nice. If you want the thrill of unwrapping presents, maybe you can ask your guests to use recycled products...old newspapers, paper grocery bags or even recycle a previously used gift bag.
It will be a little more work, but don't use disposable dishes or individual juice boxes.
As far as the goody bags, we went to a b-day party last summer where the goody bag was simply a regular size bottle of bubbles. The tag read "I'm blown away that you came to my party". The kids loved it AND there was no bag to toss. I personally loved that there was no candy involved. (My friend bought three packs of bubbles from the dollar store and divided them up for her guests).
The dollar store also sells small canvas bags if you want bigger goody bags.
I'm not sure about the decor. For my son's birthday we just hung streamers and then let him use some of the paper for art projects later, the rest was simply recycled.
Hope this helps.
Good luck with your party plans.