I use LEDs, too. And I use a "Diffusionsfolie" (someone know the english word?) over the LEDīs.
I'm working on a Vivi costume myself...how/what did you light the eyes up with? I've tried LEDs but the light is too concentrated and I can't find the right materials to make the eyes. Any help you could give would be great! Thanks!
what/how did you make the breathing bit in your face mask?