I have not used RIL post cruise so I can't speak from first hand experience but I will say that Jany is very responsive to emails and that they are very flexible in general. For specific information about itinerary for the day I would definitely just send an email.
To answer the question about leaving items in the van, while I may not have left luggage in the van, we have left personal items, purchases etc. in the van on every one of my trips with them (which is quite a few) and NEVER had any issue so yes, personal items have always been secure.
Some tours have a specific itinerary, some do not so yes, I would take a look at what they are offering and then if there are questions just email them! They are a great company!!