I didn't read what it is that you do but I'm guessing child care? Could you organise a change of clothes or take the kids swimming or start a vegie garden in the yard where they will have to change into clothes they can get dirty (you could pick up some cheap stuff from teh opp shop for them) or where you provide an art smock if they are painting or something, or organise outdoor activities where you can get fresh air?

And if worst comes to worst buy those clothes from the op shop and accidently (on purpose) spill water on the child than you will have to change them Did I really suggest that!

I've had a few people that I wanted to spew on, one client smelt very strongly or urine but her kids are too young to have weed on her! Maybe it was just her natural smell that I couldn't stand?