100mW..a bit overkill. 5~10mW is plenty for most amateur..maybe 20mW at a pinch.
Problem with cheapy OS lasers is that they have no or poor IR filtering which can make them very damaging to peoples eyes.
You do not have a "blink reflex" when exposed to these wavelengths (all invisible wavelengths) thus a laser strike on the eye ..you will not automatically have a protective "blink" thus ...damage is insidious..it's too late.
Add to this
most near IR wavelengths tends to focus on the retina so..damage can be catastrophic.
I don't think I'm overstating Laser dangers..it's just most laypersons do not understand the real hazards.