My sis and I will be in the east coast for 7 days in June. Our 1st stop will be in NJ to pick up our niece and from NJ, we're thinking of taking public transportation to DC, spend 2 days in DC and then off to NY for 3-4 days. Our niece is only 9 so we won't be doing any nightlife stuff. Any suggestions of where we should stay and do in both DC and NY that are kids friendly? Thanks in advance.