i employ hca's too and am very flexible (maybe too much sometime) but I do try to accomodate staff needs. Must say I'm not in a general hospital though - learning disability setting.
Currently I have:
a student working 3 days but guarenteed same days off for college
a dad who works two set long days
a grandma who works weekends to fall in with her dh's shift patterns and do her dd childcare.
also to add that all employers must respond appropriately to requests for flexible working of parents of under 5's.
I couldn't give every member of staff the same - otherwise I'd never fill the shifts but these three examples all fill in the bits the others prefer not to work - evenings, weekends and especially friday night.