Hi, your project seems very simple. Please, kindly take a look at my portfolio for similar projects developed in Outlook. I am an IT engineer and I work exclusively with MS-Outlook projects.
As I said, your project is actually simple to develop. It only contains two main processes in its core, which are the handling of Calendars and the Sending of Emails. So, base on that we only establish a set of rules which the Add-In is going to use to trigger the interaction of the Calendars and the sending of the emails. As you may see, it only takes two processes with few rules and that's it, you have your project ready.
Obviously, once we get this core working, the rest of the Add-In is more the common things every Add-In needs, like compatibility with x64 machines, an installer, a GUI for settings, etc.
Well, I think that is all by now. If you have any question just send a message.
Regards,
Joe.