Is there anything else included? For example will you be given meals while you're there, or perks such as paid trips out, possibly transport or similar?
Even if so, I would want at least minimum wage. £3 an hour is something I could earn easily as a student by doing things like surveys, matched betting heck, even a paper round would pay more, and you wouldn't have to cope with kids! And TWO children? My cousin is a child minder, and she charges £10 per child per hour, and the children are expected to bring their own packed lunches and pay for any extra trips.