I've been to Benodet several times - unfortunately not with the boat - though i'd love to.
As other have said Benodet is a lovely little town, with great estuary and coast to explore. lots of good beaches and fishing
Two places to launch I know of:
1) the slip in Benodet itself - wide and accessible at pretty much any state of tide, although parking may be an issue.
Slip/ beach launch al Letty - there's a fee car park right by the beach. This is tidal.
There's also a marina at Benodet, so maybe keeping the boat a float might be an option an save on launch & recovery everyday.
Various campsites / parks around. Point St Giles has some pitches where there's enough room to park a boat & trailer, and a large car park just by the office/ reception.
Member of the Macmillan Round the Isle of Wight Club