I always state "no perfume or scented lotions please :)" when I am booking, usually providers are quite accommodating and many just don't bother to wear any because it is such a common request. And yes, I also believe showering before a date is common decency for both. But if it makes you more comfortable, you can use the sandwich effect. Something nice, then your request, then something nice like "I'm looking forward to meeting you, I will arrive freshly showered and would appreciate the same :), can't wait, see you at 7:p"