No, the wavelength doesn't shift, I don't think. They do lose their brightness over time, but it's usually something like down to 1/2 after 100,000 hours. Shouldn't do any damage, those will be using UV just barely outside of the visible spectrum...Maybe if you blasted it straight into their eyes, but the same goes for visible light.
Might be better going for a UV CCFL than a bunch of LEDs, more light and better spread.