Yes. Determining the social media channel(s) where you would like your team to share content is entirely up to you.
Each update sent to Slack can include links to Twitter, Facebook, and LinkedIn, or just one or two of these channels.
If you do not want your team to share the content on a particular channel (e.g., Facebook), simply leave that template blank when creating the share request. When the share request is sent to Slack, your team members will see an option to share the content on that channel.