I suspect that there are no easy ways to get a message to Snowden or his father right now. The former is keeping a low profile and the latter is presumably a bit busy at the moment. I'd say you could try sending a message to Greenwald, Poltras, or one of the other reporters covering him, but they're likely to ignore you unless you've got something newsworthy.

That said, if you left a comment in a public and relevant place (e.g., the comments section on that NYT article), one or the other Snowden may well read it, among all the other comments.