How should I set up seating at my twinkle light and lantern-lit reception? Also, how long should it last?

I'm torn between having it start at 7 or 8:15pm. The reason being I'm having a TON of guests, like at least 275, I'm sending invites to 440! I just can't afford to have a full sit down dinner (with out doing it white trash style) for that many people. Sorry out of the question. Also I always wanted an after dark reception. The sun sets at 8:36 or something like that my research says. I'm thinking of just doing bite size "everything" sandwiches and a couple other finger foods in addition to white and milk chocolate fondue, organic bananas, Oregon fresh raspberries & strawberries, blackberries, melons, other fruits and angel food cake (which will serve as our wedding cake!) There will be a dance floor and this is being held out of doors on my parent's small acreage.