No, you still gain AAs, it is just that the easiest way to gain AAs is to do so by killing named mobs. Most of the time people accomplish this by going through all the low-end content for easy named kills that they didn't get before. The catch is they have to be xp-bearing to give AA...so you have to mentor to an appropriate level so the nameds are no longer grey. You still get AAs from quest turnins, collections and such at 80, grey or not. At 80, you also get AA xp converted from what would have been Adventure {kill} xp.

Namass, one thing to consider, the alt on your main account will gain XP faster than 2 fresh toons on the other account since you have a max level toon. Using the warlock mentored down will keep the main account from quickly and constantly outleveling the 2 new ones. You'll also get the bonus of easy travel with ports. You can always turn off xp if you're leveling too fast to get anything done.