Can you send them to before-care at the preschool so you don't need a nanny in the morning? It would be much better if you could hire someone PT for the hours they are not in preschool in the afternoons.

If you want someone to work for you in the morning and again in the afternoon, they basically can't do anything during those other hours. It's kind of unfair to ask them to only pay for the hours you need because there's a huge required split in those hours. If someone wants that kind of position, great, but I think you're going to be hard pressed to find someone who's good and does.

Is it possible someone would be willing to do some housework for you during those hours, so you'd be paying for that while the kids are in school?

OP, We'll be doing exactly this also.

We are keeping our nanny, full-time, and she will take on some light housekeeping type duties during the hours the kids are in preschool.

It is a significant expense for us, but I have the peace of mind of knowing that the nanny will be available for any sick days, school holidays, inclement weather closings, one child is sick and the other isn't, etc.... That is incredibly value and necessary for me and worth the money.

I also know that, while we won't load up her work list with enough to keep her busy full-time, having her do the grocery shopping alone, will save me a few hours a week. Add in some laundry and cleaning on top of that and I think we'll be more than satisfied.

(I should add, this nanny is perfectly willing to have the job evolve this way - it is what she has done with a couple of other long term employers before us.)

The peace of mind alone is worth the money to me (and luckily we can afford it for a year or two.)