That's assuming his friends are any more trained than him.
A lot of it is control (sigh, I typed this all last night but it somehow clicked the back button

). If I see the leg/shin shield coming up, I'm either going to go higher and go for the arms or head, or go lower (if the shield is high enough) to go for the leg. I might even turn my leg and use my foot to push the shield sideways (much more difficult, though). Otherwise, I'll try to retract the kick and go into something else. Sometimes it's hard to pull the kick and you'll hit shin to shin, and that's all part of getting your shins strengthened properly, which takes a LONG time to do safely.
Essentially, use pads when doing your Ultimate Neighborhood Championships. It'll help prevent excessive injury, because I doubt too many of you are qualified fighters that can control your blows and locks, etc, not to completely injure the other person. They're your friends, you don't want to break their ribs with their shin. Worse yet, you don't want them to do it to you! Professionals go (mostly) full-contact, amateurs don't. You aren't pro yet, so don't hurt or get hurt just because you want to be someday. Take care of yourself, man.
Safe to say, the UNC thing doesn't sound like a good idea...but maybe it's just me.
PADS PADS PADS PADS.