Are the children of their deceased father entitled to monies from his second deceased wife?

No. Generally, heirs-at-law must be related by blood or by legal adoption. Your father's second wife is not related to his children by his first wife.

If the children were legally adopted by the second wife then the answer is maybe, depending on the laws of intestacy and whether she had a will leaving her property to someone else. You can check the laws of intestacy for your state at the related question link below.