I really like the way Dan has set things up! For the interesting moment, you can manually trigger or set up a trigger campaign. If you manually trigger, you would pull in the "Interesting Moment" flow step. Something interesting to note is that you do not need to use the dropdown values for "Type". The values already there are Web, Email, Milestone. But you can change that to Trade Show, Webinar, or anything else you would like. Then you would put whatever not you would like in the "Description" field.
To create a trigger campaign, you will need a field that references the show so you can create a token to reference the show. How do the Leads that stop by get into your system? List import? FIll out a form? Scanned?