One of the best things about living in New York is all the free stuff going on during the summer. Unfortunately, that all starts the week or two following the wedding.
But if you're staying in the greater Park Slope area there is tons of stuff to do without even heading into Manhattan.
There is the Brooklyn Academy of Music (BAM) which does movies, theatre, dance, and music.
Or the Brooklyn Museum of Art. Which actually does just live up to its name.
The two main commercial strips are 5th ave and 7th ave from roughly 15th street north to Atlantic Ave. There are a lot of great bars and restaurants and boutiques here.
Citysearch and Yelp are both good resources for finding stuff you'd enjoy with photos and reviews. And I like HopStop for figuring out how to get somewhere on the subway.
Some simple tips for driving and parking in Brooklyn.
Map of Prospect Park.
Maps of Park Slope, and what it has to offer in terms of essentials, sundries, and entertainment.