Rav Moshe paskins that one may translate seforim for private use but not in a commercial fashion, that is to sell them. He said that once a particular piece of Torah has been said, it belongs to klal yisroel. With the exception of seforim which do have an intellectual property ownership to them. Translating in a blog isn’t ossur, but an English translation of Rav Moshe’s psak halocho in a published book sold to the public would be. So Wolf go ahead and learn with your son.
