I suppose my advice would depend on who you have to convince. A different strategy might be required for the staff actually working on the wards as compared to more senior managers. Not completely different, but you would stress different aspects to different people. What managers would see as important would be quality of care for patients and patient satisfaction, improved outcomes, safer discharge, more enthusiastic committed and open staff, reduced sickness rates, less incidents to report and hopefully fewer inpatient SUIs to investigate. While these are also valued by inpatient staff, for them you may want to stress being safer, being less stressed at work, the workplace being more pleasant, saving time on incident management and reporting, less unpleasant containment tasks to do, more rewarding relationships with patients.
For both groups you could pick out relevant comments from the front pager of this web site under 'responses to Safewards', or there is a powerpoint of statements collated by another forum member here:
Good luck, and let us know how you get on.