Is expiation incumbent upon someone who swore that she had not spoken about children, intending a cartoon character that was half boy, but she cannot recall whether she intended equivocation at the time of the oath or afterwards?

You are not required to offer expiation (kaffarah) because the description of "child" does not apply to a cartoon character. As for your false oath regarding not speaking about the reciter (munshid), there is no expiation required for it either, except for repentance, because it is an "oath of immersion" (yamin ghamus) for which there is no expiation according to the majority of scholars. This type of oath is strictly forbidden. Your forgetting the intention of 'tawriyah' (ambiguity/double meaning) does not affect the necessity of repentance. You should hasten to sincere repentance (tawbah nasuh) and increase in acts of obedience, for repentance erases what came before it. If you wish to be cautious and combine repentance with expiation, acting upon the Madhhab of Imam Shafi'i, there is no harm in that.