Chuck,
We are headed up for 3 nights to Harborview. (Federal Hill area) Most of the major marina's are looking for a 3 night minimum but you can check to see what they have for availability. Henderson's or Crescent may not have minimums if not full. They are in the Fells point area with plenty to do and short walk to all the Aquarium, Little Italy and all sorts of Bars and Restaurants, but no pools. Only Harbor view, Anchorage and Baltimore Marine Center in Canton have pools.
The Fireworks are on the 4th and can be seen from almost any of the marina's in the Inner Harbor.