Dawnray Archer

In a Two-Headed Giant game, a creature "attacks alone" if it's the only creature declared as an attacker by your entire team. If you control that attacking creature, your exalted abilities will trigger but your teammate's exalted abilities won't.

Some effects put creatures onto the battlefield attacking. Since those creatures were never declared as attackers, they're ignored by exalted abilities. They won't cause exalted abilities to trigger. If any exalted abilities have already triggered (because exactly one creature was declared as an attacker), those abilities will resolve as normal even though there may now be multiple attackers.

If you declare exactly one creature as an attacker, each exalted ability on each permanent you control (including, perhaps, the attacking creature itself) will trigger. The bonuses are given to the attacking creature, not to the permanent with exalted. Ultimately, the attacking creature will wind up with +1/+1 for each of your exalted abilities.