My daughter got married in January 2008 there - it was a very cold (in the 30's) snap - and for the dessert party - we decided last minute to "rent" the propane(?) heaters - like the ones you put on patios and outside restaurants - and they worked great - our guests were still able to be out side for the fireworks party but could warm up by the heaters -
I can't remember how much they charged us - but they were worth every penny - and we didn't even make the decision that we needed them until during the reception at the GF - my hubby just told the wedding planer to "make it happen" and she worked the magic - and they were at the desert party 1 hour later - way to go Jennifer O.
Best wishes on your planning - as a Disney Bride's Mom - I can say that it was the most magical thing EVER