Ok, I need a recipe for a nice summery cocktail / punch that I can make ahead and transport to a picnic. I will have some ice, a cool bag, a few ice packs and a couple of nice patterned glass bottles (with old lemonade bottle style tops on them) to transport the drinks. It's to share with friends at a boozy drinks and dips evening in a park. I don't want to do anything other than pour and serve on the night. Any ideas? I like gin, elderflower, lime...