Our family of four, including two young children 10 and under, as well as my parents, stayed at the Park Hyatt for a week during the July 4th holiday period. It was our first time in DC vacationing as a family and we wanted a hotel that was family friendly (a pool was a must!), convenient location to Metro and easy access to Georgetown, along with luxurious accommodations. Our family typically vacation in high end hotels such as Four Seasons and Ritz Carltons. Overall, I would say the Park Hyatt met all our needs mentioned above. Service was excellent. It was scorching hot during that week and everytime we came in and out of hotel, the valet was always ready with a bottle of water for us. Very friendly with the kids. We had adjoining rooms (1 Delux with a separate sitting area, and 1 regular room) under the "Awakens" package, which included daily breakfast for two. The breakfasts were huge in portions and could easily feed 4.
Negatives: Daily parking rates was $40 per day! That seemed extreme...and although the breakfast was free in the restaurant, if you preferred to dine in the room (which we did b/c of the kids) they charged a fee, which we thought wasn't very guest friendly given the rates we were paying.
Overall, good value relative to a Four Seasons or Ritz. Can't beat location, especially if you would like to venture into G'town for dinner, shopping, etc.