Hi you and your husband will have a wonderful time. I have sailed twice in the Grenadines both times from Grenada. I have not been north of the Tobago Cays but was planning to go on another cruise out of St Vincent this spring so am familiar with a potential itinerary from St V. (ended up having a crew mutiny and am going back to the BVI this spring instead!) .
1) with a captain, i wouldn't worry about the boat boys he/she will have had lots of experience may be a local and will know the harbors and boat boys probably very well. One thing you will want is to chat with them and offer a beer or a coke. They will probably try to get you to go to an establishment -bar restaurant. Also keep in mind that the captain will not need to moor at all and should be able to anchor any place you go so will not need to pay for mooring balls - confirm this with your captain...
2) your itinerary is very doable. You can sail down to Mayreau your first day distance is not that bad and wind should be on the quarter or beam. It will be a great sail!. Also consider Petite St, Vincent with a stop at Mopion island. Then you can make your way back up the island chain, to TBC, Canaoun, then head to Mustique so that you are not sailing directly into wind, current and swells. Last night I would recommend staying at Bequia as it is a short sail back to St. Vincent for a morning return. As always confirm your intentions with the Captain, see what is doable based on weather and sail conditions! I would suggest highlighting the islands you want to see - stay at and not necessarily the order and day that you want to go...keep an open mind and be flexible as all sailors must when creating a sail plan.
3) I am sure the captain will not need your help but if you want to assist I am sure he will accommodate/appreciate. Again that is something that you can establish once you meet them. Anchoring assistance may be appreciated, or snagging a mooring ball....
