Hey Becca, just writing to let you know that Campaign Monitor does support social sharing. I'm sorry to hear you weren't able to locate the tools when creating your emails. The instructions are here: https://help.campaignmonitor.com/share-campaigns-on-facebook-and-twitter
Also, if you haven't already (and assuming you're still a customer) I would suggest contacting our support team for advice regarding the ability to exclude a segment from viewing a section in a dynamic content campaign. It's possible that there's a way to do it by creating a segment of the subscribers you want to exclude, then selecting every other segment in the "Who should see this?" step. https://help.campaignmonitor.com/email-builder-dynamic-content
But it does depend on what your exclusion attributes are, it may *not* be possible, so I don't want to get your hopes up there.