In reply to djellworth:
Hi,
We (me and my 2 sons), did a very similar thing last year. On the recommendation of a friend who lives in Southsea we left our car for a week on Craneswater Avenue, anywhere around canoe lake area is fine.
Quick ride down to ferry (we did Guernsey and Jersey before St Malo and D-day beaches) and car was waiting on our return, no probs.
Have a great trip.