、。
Tomorrow morning, we need to depart early.
Literal
Tomorrow-morning, we [topic-は] early-at depart must-do.
われわれ is a formal plural 'we' — more stiff than 私たち and typical of announcements, speeches, or group leaders. 早くに is the adverbial form of 早い with に — emphasizing 'at an early [time].' 出発 ('departure') + する + ~なければならない for the 'must' construction. Formal group-leader register.