cliff that would be any normal sunny weekend in August then!

I haven't experienced any problems taking the dingy in to the Southern most beach yet, which is the least family sunbathing orientated one, but can understand the potential issue if all the boats normally anchored there decided to shift over to the more touristy beaches and plonk a tender in the middle.
re the comment about 'go somewhere else' in practice the only places to land families from small craft are either owned by the NT - Brownsea, Shell Bay and Studland or the main Poole / Bournemouth beaches. Compared to the Solent we have quiet a lot of good places really but the NT does have a very large proportion!