I think you will need the KDH 220 which is a 14 seater. The standard KDH 200 is an 8 seater which will not be large enough because it includes the driver and there will be nowhere for luggage. Confirm how many seats there are for passengers. You really do not want the exact number of seats as it will not be very comfortable.
Do you mean Nissan Caravan? Again, I think there are many different types. You would need to confirm how many passenger seats it has. There are no limits on the mountain roads. 50-seater buses use these roads everyday with no problems. However, if you choose an accommodation located on a small track then there may be some access problems.
It really depends on the size of the people and the luggage. In any case a car would be ok for a single journey. If you are planning a tour over multiple days then I would go for a van. It is worth the extra few dollars to have the space to relax. It is not comfortable to sit in the centre seat in the rear of a car and you will not have much of a view.
Hope this helps,