There are lots of ways to integrate online and offline engagement.
Online and offline methods should mirror each other with questions asked on online platforms the same as questions asked at offline events, and engagement activities online promoted at offline events. You might also wish to create a reporting back process where input gathered online is reported offline and vice versa.
Publishing photos and notes from workshops after face-to-face and offline engagements provides great content for online platforms like blogs, social media or discussion forums.