If seeing different yards means something to you I'd recommend doing the WAS/BAL swing. Camden Yards is one of the nicest parks in baseball, couple that with the surrounding area of the park being beautiful and offering a myriad of dining options. The Nats park is also nice, and Washington would offer a ton of different things to do there as well.
Plus, the Phills are at home vs the Nats on the Mon, Tues, Weds when the Jays play the Orioles. So if seeing other teams or yards interests you, you could make the 2.5 hour drive from Washington to Philly and forego one of the Jays/ Orioles games and take a game in at Citizen's Bank.
New York's an attraction on it's own that draws people and you can plan a trip in the future and catch a Mets & Yanks game while you're there.