I would say to talk to the director at your daughter's school. Let her know the situation, and that you really need to know if there is going to be an opening or not. Let her know that you would love a job there, and that that is your preferred job.
Just because your friend is working there doesn't mean that she can "get you a job". Does the job that she offered have a deadline that won't let you apply for both jobs? As far as where to send your children, I would go with your gut, which is obviously telling you to keep your daughter where she is. If you can't afford it, and get the job at MDO, then you may have to compromise for a little while, but if you can afford it, keep them where she is excelling.