Yes do it!
For parking I used Nigel at Scilly Parking. http://www.scillyparking.co.uk
Excellent collection and drop off service and totally flexible regarding cancellations due to the weather!
Luckily our crossing last year was totally flat, this was half way across!
. We saw a basking shark just outside Penzance and kamikaze dolphins half way across. Stayed at the campsite on Brhyer, again totally flexible regarding weather for crossings! Moorings available, to save taking a tender I "hired" a dinghy from Brhyer boat service to row to and from the mooring.
We stayed for four nights of a two week holiday, and the rest of the time the boat was kept at Mylor.
There's loads of info on Ribnet, do a search and it should come up.