Adeline, Catara Splendente

Although the Human tokens created by the triggered ability are attacking, they were never declared as attacking creatures (for the purposes of abilities that trigger whenever a creature attacks, for example).

Attacking with any creatures will cause Adeline's last ability to trigger. Adeline doesn't have to be among them.

The ability that defines Adeline's power works in all zones, not just the battlefield. As long as Adeline is on the battlefield (and still a creature), that ability will count Adeline itself.

Tokens will be created for each of your opponents, not just opponents that you attacked.

You choose whether each token is attacking that opponent or a planeswalker they control as those tokens enter the battlefield.