Looking for recommendations in Washington DC?

Planning a trip July 18-22.

It will be for 3 adults and 1 teen (16). Haven't decided to drive or just take the bus to DC. Bus from Philadelphia would only be about $46 for 4, then we don't have to worry about parking in DC.

This is partly as I have not decided on a hotel for our stay.
Thinking maybe
-1 room in downtown DC area (take bus to DC)
-1 (maybe 2) room in the outer-lying areas to save money, but metro fees could add up for 4 people (drive to DC)
-1 room in the outer-lying areas for the first 2 nights and then a room in the downtime DC area for the 2 weekend nights as the rates look to be relatively reasonable on weekends. I figure we can drive to DC and leave the car in the outer-lying hotel, pick it up on Sunday?

I usually travel alone so space is never much of an issue, but I'm not sure how it will work for 4 people. I'm rarely in the room so I hate to spend a lot of money on it. Definitely will need double beds (which will take out priceline hotels, but hotwire might work). bookit.com seems to have good rates when it the travel dates are like only a week out. hotels.com has a 10% coupon and there is a Visa GC offer on some stays.


Activities:
National Zoo
Smithsonians
National Mall memorials walking tour from a Living Social deal
Cruise to Mt Vernon, also from a Living Social deal
Bureau of Engraving and Printing if we can get tickets

Maybes:
White House tour- Applied, but not counting on getting it.
Spy Museum
Newseum
Madame Tussauds - Only if we run out of things to do and there is a decent discount like b1g1free.

One member of party is military if that matters.

Just looking on what might be the best hotel option for this trip and if there are recommendations for a specific hotel, that would be cool too. Some of the outer-lying hotels list DC, but then are 45min outside of DC... Along with any other activities we might want to do while in the area or discounts we can use.



Thanks