If you knew the nanny well before hand I don't see a problem.
Can you send them to your ILs instead? Missing a couple of weeks of school is ok and the school might provide work if you wish.
Or could you split it - a week with the ILs and a week with the nanny?
Club med resorts have great children's programs so you could take the kids and leave them in the creche all day and hire a baby sitter so you can have date nights too.
Some of the cruise ships might have children's programs too. A cruise in Canada and Alaska would be awesome.