Realistically you have two tasks: getting wife to go on the first charter, and secondly making it so pleasant she will want to go on subsequent sailing vacations.
A previous respondant noted that it is impossible to talk someone into doing something they really don't want to do. He is correct. Your task then is to find out what wife likes to do, and then build the charter trip around wifes desires. In the BVI there are lots of things to do, so make an inventory of what wife wants, and build the trip around her desires: She hates to make the bed in the morning - most cooks will make bunks up in the morning. She hates to cook - hire a cook. She likes to snorkle - buy the guidebook to dive spots in the Virgin Islands, and start highlighting pages. She likes to dine out - get a guidebook, and start highlighting restaurants, (what kind - Italian, barbeque, continental, seafood, etc) and there are lots of great ones down there. She likes to shop - you are in trouble, may have to go over the the USVI. Scuba dive, windsurf, historical sites, etc. If you try and sell sailing, you will lose. If you cater to your wifes desires, you may win.
A cook is probably not worth the extra money. Spend that money provisioning the boat with really great treats. $120.day will buy a lot of Brie, foie, etc.
Your second task is to make the trip so pleasant wife will want to go back again. A captain will really help with this. He will relieve you of responsibility, so there is no screaming at the foredeck to lower the anchor, etc. He will know where the spots your wife will enjoy are - and you can't figure that out from the guide books.
The trip down to the BVI is long. Experienced sailors can do it in one day. Don't. There is a motel in the airport terminal in San Juan (Best Western) which is an acceptable place to stop on the way down. That means you get the first flight out the next morning, get into the BVI late morning, and are out of the harbor by noon. The alternatives are to do a sleep aboard the first night (it will be hot - don't do it), or a room in the BVI (will be inconvenient)
I would insist on being able to communicate with the captain you hire before the trip down there. If the charter base won't set that up, go elsewhere. Tell the captain that you are the boss, and your first order to him is to make your wife happy. You might even ask for a lady skipper.
This is getting too long. I should be happy to expand if you will email me. email@example.com
It is a lot of work to figure out what one's loved one wants to do, and then accomodate to it, instead of trying to fit her into your mould, but the effort may pay off. In lots of ways.