No one has a right to a reference and a head has a duty only to provide information about a teacher's service when it is relevant to obtaining another post. You should write to this teacher to point out that it is normal courtesy to ask a potential referee in advance whether they are willing to provide a reference and to indicate that, if you do write one, it will not be entirely favourable.
In responding to the request, you can either decline to write a reference and forward factual information about the teacher's service at your school, or write a reference, bearing in mind the legal obligation to be honest and fair, making no statement which cannot be supported by documentary evidence.
DO we need a second driver with a school minibus party? We have a parent who is willing to go.
There is no requirement for two drivers with such a group, nor is there a requirement that accompanying adults must be teachers. Responsible adults are acceptable and it is the head's responsibility to ensure that the arrangements for supervision are adequate.