DC was one of my first all points paid trips. I'd highly recommend you stay within walking distance of the touristy things (Mall, smithsonians, etc.) It's so much easier to just walk out your door and walk to things. That being said we noticed at night that alot of places were closed. For this reason you might want to plan to stay somewhere where your children can swim and relax at night or plan to have a late dinner somewhere.

You'll get really good information for your trip on Trip Advisor.