Travelgrrrl.
Your travel rep at the hotel or front desk can help you with this. All tours can be arranged thru them.
Hola Kal,
We stayed at the Villa Cuba. Our hotel had a separate desk from the Airline Travel Reps for tours, which is where we booked the Van to Havana. We found our Air Transat tour rep to be completely useless, so we booked all our tours thru the other tour company.
We just mentioned to other people that we met at our resort that we wanted to rent the van, and so many people wanted to come with us, so you won't have any proplem finding other to join you. We got to tell the driver what time in the morning to come get us, so we were on our schedule. (It is still better to start early as you will loose day light later and not see as much) Would definetley recommend this to any age group.
Have fun!