It’s an interesting idea you have had and I’ve done something remotely similar but with companies and employees as a sort of CRM I’m building.
What I’ve done is go down the plugin route and utilised the WP_List_Table class as it organises things very nicely for me.
What I’m doing is creating a set of companies, in your case I’d say Individual Meetings, and then within each company, I can add people with various bits of data to go with it, so in your case that would be attendees.
I’d then have the “parent” meeting type as an additional piece of meta data or even save it under a custom taxonomy to retain the core functionality of getting the various meeting types with a standard loop and category option.
By using WP_List_Table, it keeps things nicely organised and adds the ability to sort by column with whatever meta data you so wish.
WP_List_Table documentation is severely lacking and the resources via Google searches are all wrong and it was through combining various bits from each article researched I got it all working.
I’d be more than happy to send you the plugin so you can view it in action and it might give you an idea on an approach. Plus, you’ll have a good base to start from.
Let me know. 🙂