Can you charge them a part-time rate, maybe $5 more a day if they are using less than 5 days/week. That's what I do. Also, are they going to be scheduling around stat days so they get out of paying for them? That's been my experience with part-time families. No, you can never fill the empty one day/week space unless you are incredibly lucky, I agree.

I know some people charge for full weeks even for part-time families or they keep interviewing. Personally, I like to have one part-time family so I have an easier day or two a week with only 4 children, but that's me. Do what is best for YOU!