It is important to note that you can share activities with others, whether they have Shoelace or not. You will not necessarily have to create a Facebook event to engage people.
Do not expect to try Shoelace for a moment. At the present time, there is only invitation, and only in New York. Whether it becomes public or not will probably depend on its initial performance. If nothing else, it's a relatively recent take for a social network created by Google: it's trying to get out of your phone instead of hanging.