If there is anyway they can justify the extra expense to get into a turboprop it would be well worth it. The problem with the older recips is they are older. Unless you get into a very well maintained ship it can be a pain.
If they are open to a single engine turboprop look at a 10 year old Meridian. They are weight limited but if you are only going a few hundred miles there will plenty of useful load saved from fuel and it would work great. The Caravans are still over a million and not pressurized. The older Meridians are around $800K to $900K. Good luck.