I would skip DC for fireworks for 4th of july. Instead come up to Baltimore. You can get dockage and there are 3 different sets of fireworks that go off at the same time . 1 set over Ft McHenry, 1 set near fells point, and 1 set at inner harbor. Almost anywhere in the harbor you can see at least 2 if not all 3 sets.
Besides Ft McHenry( home of battle of baltimore) and the star spangled bouey are all good. (Only red white and blue official US waterways mark it is approximatly where Francis Scott Keys boat was when he was watching the battlle of Baltimore. He was a Georgetown lawyer who had been sent up to negotiate for the hostages who had been taken during the sacking of Georgetown and DC. His boat was put under the control of a group of British Marines so that he did not warn the citizens of Baltimore. The citizens of Baltimore however found out and sunk a bunch of old hulks of crummy ships along what is teh narrow section between Ft MCHenry and the other side of the shore. They then battled for days and Baltimore won. At that point the British sunk away in defeat and headed down to New Orleans where since they had previously captured the brother of the biggest pirate in the area the pirate band headed by lefoot joined with the USA and fought the battle of New Orleans.