I have family down in Swanage and growing up I couldn't wait to get down there for the carnival week, usually it's jam packed, but very much worth looking down there for a family day or weekend away, there will be loads going on, some of the events are chargeable but they are usually a couple of pound, most of the events are free and all donations go to chairty.
The beach and town are very clean, great quirky shops, awesome fish and chips and of course punch and judy on the beach. Absolutely stacks to visit in the local area, Old Harry Rocks, Sandbanks, Corfe Castle, The old Swanage Pier, Swanage Lighthouse, Swanage Railway.
A bit about the week:
Swanage Regatta and Carnival is the premier carnival on the South Coast.
Swanage Carnival 2008 Over 100 events take place during Swanage Carnival week, there is something for everyone:- live music every day, the half marathon, sand castle competitions, the sailing regatta, treasure hunts, magnificent firework displays and not forgetting one of the longest processions around.
Hope this helps someone who might be looking for something to do in a weeks time, I'm sure once you go you'll go back for years.
another good website for info on Swanage:http://www.virtual-swanage.co.uk