A day on the other side of the water, where the landscape changes completely within four minutes of leaving Poole.
Morning: the crossing
The chain ferry from Sandbanks crosses the harbour entrance in about four minutes and lands you in a different world: heath, dunes and National Trust coastline. Note the vehicle restrictions if you are bringing a coach.
Midday: Studland
Studland has miles of sand backed by dunes and heath, with views back across the harbour mouth to Sandbanks.
Afternoon: Old Harry Rocks
The coast path south leads to Old Harry Rocks, the chalk stacks that mark the eastern end of the Jurassic Coast. Roughly a mile and a half each way from Studland, mostly level with a gentle climb.
Back
Return by ferry, or extend to Corfe Castle if the day allows.
Wear proper footwear and take a windproof layer: the headland is exposed whatever the forecast said in town.