This is the 3075th most frequent French word.
occupés
"Occupés" means "busy" or "occupied" in English.
In this sentence, 'occupés' is used as an adjective to describe the children being engaged in activities (doing homework).
Les enfants sont très occupés avec leurs devoirs.
The children are very busy with their homework.
Here, 'occupés' functions to convey that the subject (we) are actively involved in the action of preparing.
Nous sommes occupés à préparer la fête.
We are busy preparing the party.
In this case, 'occupés' indicates the state of the seats, meaning they are not taken or filled by anyone.