I went to Aruba for 5 days in April in 2010 and then for my wedding in July 2011. In April 2010, it rained multiple days, maybe 3. but a rainy day meant 1 or 2 bouts of rain that would last MAX 5 minutes. The rain was also very light. In July 2011, there was only 1 days with a sad excuse for rain. By "a sad excuse for rain," I mean that I felt the rain on my skin, but the drops were so tiny that I didn't see them in the sky and they didn't make anything look wet. I really wouldn't worry about the rain for your August wedding!
We didn't get married at the Renaissance, but we used Tito as the DJ. We provided him with a REALLY comprehensive list of songs. We included a lot of Italian songs. Since we weren't sure of he'd be able to easily download them, we gave our wedding planner a CD with the songs. She passed it along to Tito, and it worked out well. He did a good job of gauging the guests' reactions and adjusting the type of music that he chose from the list we gave him. He also was very receptive to our requests for specific songs or changing the genre. Overall, he did a really good job and was easy to work with.