This is Hagley, an old DuPont estate in Wilmington, DE. The grounds are just beautiful, particularly around this French-style garden. I can imagine a beautiful spring family-style dinner reception at dusk with lots of champagne, sorbet, candle-lit paths, and twinkle lights/paper lanterns in the trees.
My reception will be a little too large for a tent rental. But if you're planning a more intimate affair. How about a place like this?