Well, you'll be going during the the middle of summer so expect it to be crowded. Your only saving grace is that you're going mid-week. It's even more crowded on the weekends.
My advice is what everyone else advises at any of the Disney parks during the high season: Be there at opening and hit the popular rides first, get fastpasses (get to know which ones are independent of the system for multiple fastpasses), go back to your hotel for a swim when the crowds get really thick and return later in the day to enjoy the parades/fantasmic and other rides.
They will allow you into Main Street up to 1/2 hour before the offical opening time. The Matterhorn, Dumbo, and Peter Pan do not have fast pass and their lines get longer as the day progresses so think about doing those first (or skipping them if no one in your party is interested). Get a fast pass for Splash Mountain early in the day before they run out.
Oh, if you want to see Fantasmic, you'll have to stake out a place 2 to 3 hours in advance for the first show. If there is a second show, you'll probably be able to slip into a decent viewing spot as the crowds from the first show leave.
Read through the boards and you'll probably pick up other interesting tips.
Hope that helps.
