Must you attend a conference to attend/present at an affiliated event?
Is it possible to attend/be published at only affiliated events and skip the conference?


This depends a bit on the conference, but in most cases, the relationship between a "main" conference and its satellites and workshops seems to be like this: 


Nobody really cares whether you actually attend the main conference, and there is no reason to be quiet about this. However, some conferences require you to register (I.e., pay) for the main conference in addition to any satellite events, even if you have no intention of attending. So you should keep this, probably significant, additional costs in mind.
Satellite conferences often have their own proceedings, so it is definitely possible to be published only at the satellite, for whatever that is worth. Associated workshops often publish their proceedings in a companion volume of the main conference. I am not sure whether you would consider this "be published at the main conference", or why this would matter for you.


That being said, the best persons to answer this for you reliably are the organizers of either the main event, or of the satellite events you wish to attend.