Sorry, but I disagree. The separate config settings are for specific technical reasons, due to previous user feedback, and for backwards compatibility purposes. We have two config settings for Events and Holidays due to Events turning on Akonadi which many people don't want to use but still want to have Holidays displayed. Until we have a proper solution to the Akonadi problem we have to retain the separate config options. In any case, the solution would be in modifying the behaviour of the GUI, not in changing the backend config.
We used to have separate tick-boxes in the GUI directly mapped to the config options, but I changed the Holidays tick-box to the multiple holidays selection widget and had to retain the backwards compatible behaviour of respecting any existing config setting. You also have the usability issue of people ticking the Holiday options but not the Event box and wondering why the Holidays don't show, you would need to change the GUI to make this obvious.
Also, you seem to have other unrelated code fixes included in the review?