Philip Seymour Hoffman -- Family Leave for Wake

Philip Seymour Hoffman's family left their NYC apartment Thursday afternoon ... presumably to attend the actor's wake.

Mimi O'Donnell watched over the three kids she had with Hoffman as they made their way to the Frank E. Campbell Funeral Home on Madison Avenue.

The wake will be held from 5 - 9 PM EST.

A funeral service will be held tomorrow at the St. Ignatius of Loyola Church on Park Avenue. The service will be small and private -- only family and close friends.