Muggles wrote ... on Wed, 06 Apr 2016 23:21:33 -0500 ...

Well, are they just barely teens, or older teens?

One is 19, the other 12.

What is your usual method of discipline?

Discipline? I don't think that applies here, since this is
volunteer work. But discipline is almost never anything more
than a reprimand. Never have they ever been hit. Never have
we had to punish them other than to perhaps ground the older
one for a day or two and withhold things they care about
for a short period of time (classic TEASPOT method that
everyone is taught in child psychology).

What motivates them, and what life skills do they lack?

One is on the computer 24/7 and the other is on the phone
24/7. One kills aliens day after day after day, while the
other fusses over her hair and nails and clothes.

Typical stuff. Very typical stuff.