Correct. Outside of scope. I routinely publish gists of example code, but that example code is just that, an example. We’re happy to provide examples where possible, but supporting custom development and extending examples into production ready code is outside the scope of support.
With regards to the proceed to checkout link, you’ll find examples of how the Multi Event Registration plugin handles displaying the link conditionally (in the mini cart widget, for example, if nothing in the cart, the link doesn’t display) Here’s a link to the source code: