I don't work. Lucky me aye.
I do offer to look after the children of working mums from time to time, so don't discount the option of school or kinder friends being happy to help. I genuinely feel that adding an additional child (or two if they are well known) makes very little difference to my day. It's no trouble.
I am hoping this will be an option once both mine are at school (so I don't have the issue of paying for daycare for DS while I am not at work) - I would be more than happy to mix and match and take peoples kids some days and they reciprocate etc. I think is a good option - and I agree that once probably kinder and up age that adding more children doesn't make too much difference and in some ways makes life easier.