I would get the 400nm for playing around with. The cost is less that way. You can do almost the same things with the 400nm.
385nm is good for a couple more things like fillings and human urine.
Cat urine will glow with either. So will scorps, dollar bill strips, credit cards, special inks, white shirts, glow in the dark, etc.
Oh, remind him nto to shine it in any ones eyes as it is harmful. This is why sunglasses block UV, because otherwise yoru pupil would be wide open to the UV light. Bright sun and your pupil closes down.