This question is really better asked of horary astrology, which has specific parameters for whether someone will conceive, and how many children they're likely to have (but only in terms of one, one or two, a few or lots, not exact numbers). In John Frawley's book The Horary Textbook, he mentions that William Lilly, probably the most famous of all horary astrologers, would have said that trying to exactly predict the number of children is "too scrupulous a quere." I think it's "too scrupulous" for tarot as well, and perhaps even more so. I would most likely refer the querent to a horary practitioner if I knew of one in the area.
When I start a reading, I tell a sitter that I consider tarot to be a way to promote self-understanding and increase awareness of one's circumstances, that it can be predictive mainly to the extent that we create our own future through the actions and attitudes we adopt, and in that sense it can help clarify what those might be. I have more hesitation about the "timing" aspect that may come up, since we all know how tenuous the conventions are for that.
