Mark, you'll love it!
We didn't bother to camp on St Mary's as the campsite is up a hill and trolleys would have been even more kit, of course you could use your Lazee Lizard but I guess you're not tall enough. :rollin
We paddled straight from St Mary's harbour to St Martin's, it's only a mile or so, and the campsite on St Martin's is almost on the beach, a lovely spot.
We used OS Explorer (1:25,000) map 101, Isles of Scilly, as well as the Admiralty Chart of the Scillies which is the same scale. The campsites are marked on the chart.
There's lots of info on
www.scillyonline.co.uk www.simplyscilly.co.uk www.pzcc.net (Penzance Canoe Club)
St Martins Bakery is a place not to be missed, or to avoid, depending on your point of view!
Sue