@mikado1 - your friends run the risk of an employment rights tribunal and subsequent pay out.
See article here: www.google.co.uk/amp/s/www.irishtimes.com/life-and-style/health-family/as-employment-rights-change-has-the-au-pair-had-her-day-1.2951047%3fmode=amp
It is 100% the case au pairs should be treated as other employees, there's undoubtedly abuses that still go in but it's being increasingly enforced.
Re: after school care costs etc- we find it varies hugely between friends in Dublin, I think a lot depends on the given primary school. Also whether or not you need before school and after school, or can get away with just after school. You're costing up a move to Dublin, but do you have a clear area/school in mind? Basically we've one set of friends who have to drive to childminder, drop child off at 8am, childminder gives breakfast and brings child to school, they drive home then get luas into work, get home and pick up from childminder at 6.30. They pay lots more than other friends who are walking distance to the school and can have one parent do drop off, then the primary school runs an after-school club and they're able to pick up from that at 5.30/6. One parent does mornings the other evenings. Some schools seem to have after school provisions which are cheaper, also living walking distance to school (and in our case work) seems incredibly helpful in terms of how many hours you need.
Crèche costs also vary depending on area - friends in rathmines are paying 1300 for one child (one year old), friends in another part of south Dublin a grand, so I think to get realistic coatings you need to know your area, likely commuting costs, etc.
IME, costs like electricity, utilities, car insurance, groceries etc don't vary so much across Ireland, but childcare, eating out, children's activities seem to be much dearer in Dublin, but within Dublin there's still huge variation. For us, talking to friends about cost of childcare was really handy for getting an accurate picture and helped us focus in on where to live, but the hardest thing was getting an idea of how much our spending on utilities and groceries would change from London to Dublin as people have different habits, ways of living etc and it's hard to figure out an exact equivalent.