Cairnwood was under the $2,000 if you are willing to do a weekday (was about $1,600 in 2009), and it is definitely upscale. To keep the budget down maybe consider not putting up a tent, so have the whole party in the house. For dining a party of no more than 75 that works, for more you'd have to split up the dining into separate rooms or do stations (which can be fun).
Society Hill Dance Academy!
The Saturday Club in Wayne is only $1500 I believe and can seat up to about 110. Fireplace and high ceiling with exposed beams would decorate really nicely! http://www.saturdayclub.org/club-house-rentals.php
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