That's a tough one, as he hasn't actually done anything improper, but I personally would still say something. Ultimately your child is being put under the care of an adult that you feel uncomfortable with. I would put it in writing and mention specifically his rudeness, and that your daughter has spoken about how uncomfortable he makes her. He probably isn't a paedophile creep, even though he gives you the heebies. But if it came to something happening on the bus (e.g. flat tyre) how much do you trust he would act in the interests of the children, being the only responsible adult there at the time? If you don't trust that in those quite possible scenarios that he could be trusted to take care of the kids adequately then I think you are within your rights to lodge a letter.