A) I presume that this is information which is known only to you and possibly not officially.
Without knowing why the children are deemed to be at risk, it would be very difficult to advise you.
One can only play it "by the book", working on the assumption, not necessarily unreasonable, that someone who has difficulties in the role of parent need not automatically be unfitted to teach. The reverse is also true!
If there is anything about this teacher's conduct towards pupils in the school which gives cause for concern, you will need to monitor his or her work very carefully and be ready to take appropriate action if necessary. If there is nothing out of the ordinary, you have no reason to treat him or her any differently from other members of your staff.
If there is any suggestion of child abuse attaching to this case, you should seek the advice of the Child Protection Agency, which is presumably aware of the case anyway.
Q) Must a school provide a place for staff who wish to smoke?
A) No. Although the prospect of teachers joining Year l0 pupils behind the bike sheds is not attractive, no employer has a legal obligation to provide such a facility.
Indeed, some local authorities have declared all their premises to be non-smoking areas.
While not every employer might wish to go as far as that, it would be imprudent not to ensure that those who wish to work or relax in a smoke-free environment may do so. In many schools, it is simply not possible to find another room which can be dedicated to the smokers: that may well decide the issue.