Is Wappinger too far from NYC for a fun day trip with the family?

It's an hour and a half drive. If you take the train it's $50. bucks round trip. If your doing a play yes if you want to spend time no it's far.

No. You're probably looking at an hour and a half drive one-way, and as someone who did a very similar trip MANY times in my youth, I think most kids will be able to handle the car ride. If it was in the northern parts of Dutchess County, I'd say it might be too far for the effort but in Wappinger I wouldn't have an issue.

Even if you're just doing something simple like going to a ball game, the stadiums are right off highways and aren't horribly long trips.

I think it is doable. I guess it depends how young the kids are and if they can deal with an hour and thirty-five minute train ride. That's the commute time from the nearby Metro North train station in New Hamburg, NY, about 2.5 miles from Wappinger.