Lawyers dealing with public law Children Act work may be representing the parents or other carers of children subject to a section 31 application.
In contract law, the lawyer's obligations are to his/her client to deliver the relevant service. A duty of care indicates a liability, including for damages in negligence (as opposed to contract).
Professional conduct obligations are a matter for the Law Society. The Professional Conduct Rules are set out in the Guide to the Professional Conduct of Solicitors published by the Law Society.
The Law Society's Good Practice in ChildCare Cases says
Solicitors must ensure that the principle that a child's interests are paramount is reflected in the conduct of the case itself. Solicitors acting for local authorities, for parents and other adult parties, or for the child or children's guardian, giving instructions on the child's behalf, all have a duty to act on the instructions of their particular client. Each client may have a different view on the child's interests. However, all solicitors can, and should, adopt a child-focused approach by ensuring that the presentation of their client's case takes into account the needs of the child throughout."