With kids, give Guided City Bike Tour (e.g. Fat Tire Tours) a miss.
Berlin is flat, bike-friendly and so spread out that a guided ride genuinely connects the dots better than walking — and a good guide turns a list of sights into a Cold-War-and-reunification narrative you'd otherwise miss. The most established operator, Fat Tire Tours, runs from the base of the Fernsehturm on Alexanderplatz and offers both a broad city loop (Brandenburg Gate, Checkpoint Charlie, Wall) and a dedicated Wall route out to the East Side Gallery, a border watchtower and the Treptower Soviet memorial. The catch: it lives and dies on weather and your saddle stamina, group pace can drag for fast riders, and confident independent cyclists who've read up don't need the guide — Tempelhofer Feld is the free DIY alternative.