Have you tried probate records for Anderson Co, TX? Everton's "Handy Book for Genealogists", shows Anderson Co, Tx has probate records from 1846 (county formed in 1846). You might check orphan court records, too. Even though the mother lives, the court may appoint a guardian for the children, especially if there is any estate (land etc.) that they might be in line to inherit. Sometimes the mother is allowed to be appointed their guardian. But, in either case, some mention of the death date of Charles may be included. Also, check out land records, if it stays in the family it may not be recorded til it goes out of the family.