Where should I stay if planning a vacation to Washington DC?

Okay I am so lost. For days I have been trying to plan a family trip to DC. I want to take my son to the National Zoo, State Capitol, etc. My problem is should I be looking for a hotel in DC or would I need to stay someplace outside of DC like VIrginia. We are driving so I would prefer staying someplace close to all attractions. Is this possible? Oh and is the Traffic going to be terrible?? PLease help . Thanks