Why not serve refreshments in bottles or cans that can be easily disposed of after the party? Bottled beer or wine colors, cans of soda and bottled water? You could present in them in pretty bins or galvanized tins filled with ice and perhaps decorated with ribbon. Guests can serve themselves and you can set up areas for them to recycle their empty containers. This would fit perfectly with an outdoor theme and will make for easy, stress-free clean up for you afterwards.

Good luck!