When in June are you planning your trip? Anytime near Memorial Day weekend or the last few days before July 4th are expensive.
Hotels are also more expensive during the week instead of like the normal weekend. If you could swing staying Friday through the weekend and even a day or two into the week would save you money. The metro is halfprice on the weekends and free parking at the metro.
Hotels in Old Town Alexandria are really nice and they have a huge Embassy Suites right near the King Street metro. You can walk to it with no problems though I don't know how much parking is.
One book that I recommend and still use living here is the DC for Dummies guide.
I agree with all of this. The Embassy Suites in Alexandria is perfect. Don't discount the fact that they give you a nice breakfast with the room. Food in DC is VERY expensive-breakfast will cost you close to $50 for the 5 of you at just a plain old breakfast place like Perkins. The really nice thing about Alexandria is that you can take the free trolley into downtown and bum around there in the evenings. It is very safe and a lot of fun shops/restaurants, etc.
You can also take the metro right from Reagan to the hotel-luggage and all--so you don't need a car. The metro is VERY easy to use and half the fun of going to DC. We got week-long unlimited passes when we were there because you will want it for getting around town too. We also took it as far as we could then hopped on a bus to go to Mount Vernon-again, VERY easy to do.