We did a round trip from SV (I believe it was Blue Lagoon) several years ago. Stopped at Mustique, Mayreaux, the Tobago Cays, Petit St. Vincent, Union Island, Bequia and back. It's much more sporty sailing than in the BVI. Bigger seas, higher winds, tighter anchorages. No mooring balls generally, so being comfortable anchoring in a tight spot is a must. The boat boys are no problem, but security is a bit dicier than in the Virgin Islands. You have to lock your dinghy motor nightly, lock your cabin when you go ashore, etc. There have been several instances of cruisers getting boarded and assaulted in the middle of the night in SVG. To be fair, I've not heard of any attacks on bareboaters. The islands in general are poorer and grittier than the BVI, and they are not totally set up for yachting tourism like the BVI. You have to watch your fresh water more carefully, although most of the yachts now probably have water and ice makers.

I very much enjoyed the sailing down there. It's beautiful, but you have to do more preparation. There are a couple of long sails down and back (not to mention the 7 hour open water sail if you depart from St. Vincent). I'd definitely do SV-Grenada one way. Personally, I would not sail there with just my wife. I'd want one or two more men on board, and I would not ever anchor in an anchorage where I was the only boat. It's safe down there, but requires more caution.