What is the right course of action?

You chose to stop because a man wants to cross the pedestrian crossing, which is the correct action according to German traffic rules. When approaching a marked pedestrian crossing (Zebrastreifen), drivers must give way to pedestrians who clearly intend to cross or are already on the crossing. This means you must reduce speed early and be prepared to stop to let them cross safely.

Continuing to drive slowly because there is no indication of a pedestrian wanting to cross is incorrect if a pedestrian is visibly waiting or signaling to cross. Also, stopping specifically because of a child behind a van is only necessary if the child is actually intending to step onto the road and is visible to you.

The key rule is: at a pedestrian crossing, always yield to pedestrians who want to cross and stop safely before the hold line. This ensures pedestrian safety and complies with § 26 of the German traffic regulations (StVO).