I wonder, Prince_Lieven. I really do. Part of me believes they would behave in the way you mentioned, but the other part thinks that they would be highly reserved, sizing everyone up before speaking too freely. As a good hostess, I would definitely have talking points prepared to encourage the sharing of experiences while enforcing that we respect one another.
I think the "younger" royals (e.g., Mary, Alexandra, Maria, Victoria...all from my guest list) would be fascinated (along with me of course) to hear from the "older" royals (e.g., Catherine the Great, Elizabeth I) and vice versa.
Many of my picks are female. It would be nice to think that there would be a mutual admiration between them. Maybe I'm being a little too positive...who knows!!! It would be an incredible evening nonetheless. Let the Cristal champagne flow!!!