A. The rules and laws on social media are evolving all the time. Your question centers on two issues: First, who controls the company’s confidential information? You can easily require employees to treat confidential information, such as the planned opening of a new location, quiet until you are ready to so announce.
A slightly harder question: Who owns the company’s name and presence on social media? I can’t tell whether your employees are pretending to represent your company or if they simply mention that they are employed by your company. The first activity is problematic and possibly illegal, depending on what steps you have taken to trademark your organization’s identity. You may have far less luck asking employees to remove references to their place of employment from their own social media accounts. Employees may even have the right to complain about your organization with co-workers under the current National Labor Relations Board’s interpretation of what it means to “engage in concerted activity.”
I’d suggest you show social media postings that concern you to a local attorney and formulate a policy to protect your confidential info.