Should we move our wedding date?

We're due to get married on the 30th of August in wiltshire (England) and have decided to do away with the marquee and brave the elements with a picnic/hog roast reception. We're thinking very strongly about moving the date forward to the 16th to try and increase our chances of good weather. We were just wondering if anyone can think of a good reason or something we haven't thought about for either date's pros or cons. We have to let the vicar know tomorrow so any hints, tips or advice would be wonderful. Thank you