Recurring events are complex. Really complex. You may want to ditch them altogether and put in the instances individually - as you are doing this by code then that shouldn't take much effort (certainly less that writing code that can work with recurring events.)
If you're fearless then you need to understand how SharePoint stores recurring events :-
There is a master "Series" record - something like "Event X, 10am to noon on the first Monday of each month"
Then you have "event exception" records - so if you change one event instance from Monday to Tuesday (or in your case update details of the individual visit) this event exception will say something like "The instance of this master event that was due to take place on this date is now replaced by this"
In effect this means that to remove an instance of an event you actually insert a new record.
This is the single best resource for how this works, though he is only talking about reading the recurring event data.
If you play around with a calendar and keep switching to the "All Events" view you will get a feel for how it works.