FYI: I have seen the "live volcano" on St Lucia, and it is nothing more than a sulpher-smelling mudhole where a few bubbles (of sulfar gas) rise to the surface abd break once in awhile. It is nothing like a volcano, more like a mudbath at a hot springs - exept you can't go in.
Basically, you would look for about a minute and say "OK, I've seen it."
I really don't mean to sound dismissive to your concern, I am only saying to tell you that you are not missing as much as you may think you are. A banana plantation, well, bananas even grow in Florida, and as for the banana ketchup - I can't help you there.
St Lucia is a beatiful island and I hope you make it back someday, but honestly, please don't let this little change ruin your cruise, because you are not missing as much as you may think.
Here is an excerpt & picture:
"The St Lucia volcano, also called the St Lucia sulphur springs is said to be the only drive-in volcano in the world. The last minor eruption occurred in the late1700’s. It was only a steam eruption but not one with magma and ash."