The question is: How is the job to be done?
You don't understand Isobel, but I do.

If her back is put up, wild horses won't move her.

She'd snap her fingers in my face, and tell me to go to a place that you are better acquainted with than I am, or will be, and take my money with me.

Of course, I could hold her for a few months, till she is of age perhaps, but after that, No.

So it seems that the only chance is your son.