I think the appropriateness of bringing children into work completely depends on:
a What the workplace is and whether having children there would be a H&S issue
b Whether it would disrupt or disturb other staff
c Whether the workplace public liability insurance would cover the company, if for example the child fell over and got injured
I've worked in an environment for years where staff often bring their kids in if their childcare fails during school holidays. The children just sit quietly and do work/sit on a computer for a while.
As a manager I would always agree to this as I would rather have the team member in work than having to take a day's leave unneccessarily.If the child was disruptive however, I would ask that they remove them.
We even had a Board member bring his son in once, as the Board meeting was late afternoon and otherwise the Board member would not have been able to attend.
I think all mine have been into work with me at some point, either on the breast or sitting in the corner doing something quietly
My sister used to take her daughter to work everyday during school hols, otherwise she wouldn't have been able to work.She worked in an art gallery and visitors used to love meeting her five year old (she also took her in as a baby to BF her - this was 18 years ago as my neice is at Uni now)
Public liability insurance should cover having minors in the building.
There would be some environments it wouldn't be appropriate, for example in busy industrial environments where there is machinery operating etc
Its a judgement call really on the part of the manager of that workplace