Renting a villa depends on your budget really, not the number of people traveling. There are only two of us and we always try to rent a house in most places we travel. Many are priced according to the number of people staying, regardless of the size of the house or number of bedrooms. If you go to some of the websites for rental properties (and there are many) for SJ you will usually find a place where you can shop according to number of bedrooms or price. There are also condos and some smaller guesthouses. Don't forget to check vrbo and homeaway type sites as well as realtors. There are hundreds of rental properties so it all boils down to choosing a location and deciding on what you want to spend. Have fun shopping and have a great trip!
Others who travel there frequently can give you specific suggestions.

Agree, there's no reason why the two of you can't rent a villa, if your budget allows. However, your post says you want to be "pampered" and that won't happen at most villas since other than a housekeeper who comes in to clean and make the beds there isn't a staff to do the "pampering". You could hire a chef to do your cooking and perhaps a butler to bring you drinks, etc. but that will certainly add dramatically to your costs. If you want to be "pampered" your best bet is to go to a full service resort where they have the staff and the necessary "facilities" to give you all the pampering you want.

HI - We are in your age group & have been holidaying in STJ for 20+ years - Our favorite island hands down. There are many options for staying in STJ - From luxury Villas & Caneel to quaint Bed/Breakfast/Inns & Camping. It is a small island with some of the most breathtakingly beautiful beaches/water in the world. The town is walkable with great Beach Bars and some good eats. There is so much 'exercise' activities all around. Honestly, we like to just rent a villa (from 1bedroom to 3) at the Westin, from an owner - you get fantastic deals, a fabulous 1/4 pool & lots of little perks/extras that you can't get renting a Regular Villa. You can also rent a Jeep on-site for all your excursions. Groceries, Spa, Tennis, Water Toys, Restaurant right there. We actually like hiking to town from the Westin. Its quiet & nice. Bypass STT, way to touristy!
You won't go wrong with STJ!!

Just because you rent a villa doesn't mean you have to eat your meals there. There are plenty of good places to eat out on SJ. I am sure you can also hire someone to come to your rental for massages, etc. I think having a beautiful house with plenty of room and privacy, a pool, and a gorgeous view is hard to beat.

Rent a villa and a jeep! Make sure you understand that many of the villas offer a cheaper rate for two people - and they simply lock off the extra bedrooms. You'll love the privacy, and in many cases it's cheaper than Caneel. Westin has too many kids for my taste.

Have fun!