all employers must consider the needs of employees with families of children under 5yrs old - law now is for X weeks (sorry not sure what it is) per year as emergency carers leave can be taken and must be honoured by employers as unpaid leave. some employers as mine, within reason, pay carers leave in these circumstances.
we have an emergency childminder within our contract but would envisage only using this when something happened whilst children are in cm care - e.g. other child requires A&E attention and mine go to other cm whilst I'm getting back from work.
If our CM went sick then DH or I would stay at home or do a shorter day, leaving children with grandparents.