Since your question is related to licensing what I can suggest is that you contact our sales team at firstname.lastname@example.org
or directly your account manager and provide a list of all sub-domains along with your primary domain, which is already registered with the license. They will be glad to help you with this.
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Sitefinity CMS Ideas&Feedback Portal
and vote to affect the priority of the items