The land immediately around Poole is built up, so camping means heading for the harbour's edges or crossing the water, which is no hardship.
Across the harbour
The Isle of Purbeck has the best of it: sites within walking distance of Studland's beaches, the heath at Arne and Corfe Castle, with the chain ferry putting you back in Poole in minutes.
Around the harbour
Sites on the northern and western shores are handy for Upton Country Park and the Wareham side of the water.
Glamping
Safari tents, pods, yurts and shepherd's huts are widely available, and book earliest for school holidays. See also caravan and holiday parks.