Hi Jan,
I would hope that as you have kept the lines of communication open with your clients, that they should not mind you calling to say that their cleaner has gone sick.....as long as you either say to them that another cleaner or yourself will call later that day (if that is possible) to do the cleaning, or offer them a slot the next day if poss.
With the staff, they can't help it if they are sick of course. However, the problem is when they take advantage of their boss and call in sick when they want a day off. Am I supposing correctly that you do not pay them on sick days? If you do, then maybe it would be worth while starting up some sort of scheme where if they have not been sick or late for say 3 months or so, they are rewarded i.e extra few hours on their wages.....or whatever. This may give them an incentive to come in!!
Might be worth a go?
You should also have in your contract with the staff that they have to give at least 1 or 2 weeks notice before they go....to give you a fighting chance to get a replacement.
Also, a few postings ago, one of the chaps always had 1 member of staff extra to what he needed, as someone was always off sick or on holiday. As you get bigger, may be worth looking into.
All the best
Tim