We are getting into the minutiae of the law but I think if you intend something reasonable it is not reckless under the law. So driving 120 miles per hour and hurting someone is reckless. Or doing something else completely stupid and hurting someone.
Assuming his intention was to knock away a cup that would probably not be considered reckless. As long as you consider that in and of itself a reasonable action then no he still wouldn't be charged.
Here is what wiki defines as reckless:
I might be guilty of getting too far into detail like you said. However, I do not see how it is reasonable to attempt to dislodge a cup of coffee using force sufficient enough to knock an adult to the ground. It's a coffee cup.
Also keep in mind the law does not go by wiki definitions. I can't find a legal definition for reckless under PA law. I should note that reckless driving somewhat defines it as (paraphrasing; closed the page) willful or wanton disregard for the safety of others.
In this case, I could see an accidental strike to the woman's face if she were sipping from the cup at the time. Yet, that is both willful and wanton disregard for her safety. If she were carrying the cup at waist level, as most people do, then he missed his mark by several feet. I'd be willing to call BS on his claim.