Rompedores de Jaula de Kessig

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

You count the number of creature cards in your graveyard when the triggered ability resolves.

You declare which player or planeswalker each token is attacking as you put it onto the battlefield. It doesn't have to be the same player or planeswalker Kessig Cagebreakers is attacking.