It will be fairly crowded, but probably not crazy crowded. Wednesday is the best choice for day of the week, and DL will still have the 8AM-Midnight hours. If you can plan your day to be there the first and last two hours of the day, you will get on a lot more rides.
I've gone every summer during the week over the last several years. It's always been crowded but not out of control. Several of my friends have gone this summer and said it hasn't been much different from years past. It's no secret, show up before opening, stay until the crowds become unbearable (usually around 12:00), head back to the hotel for a nap/swim. Return to DL sometime after 5 or 6 - it will still be crowded but after relaxing for a few hours it isn't so bad. The first and last two hours the park is open have always been the best for me. DCA is a nice alternative to the crowding @ DL in the afternoon.