Connected Onboarding Solution - how to clear out old tasks?

I'm using the connected onboarding solution for a demo and there are a bunch of really old tasks showing up in the My Tasks and Group Tasks view.  I thought if I cancelled the onboarding, it would clear out related tasks, but it didn't.  Now i'm stuck with a bunch of orphan tasks in the user interface which makes for a pretty messy demo.  How can I safely get rid of old tasks from the UI?