Maybe both. Tell people what can be gleaned in a general sense if they choose to have their characters participate, but "pull from a hat" or whatever the amount that get detailed threads?

I, myself, am often happy to take general info and assume from there, but I'd be a bit disappointed being excluded from that portion of the event entirely.

That said, it depends on the event. I honestly don't know how character-specific the turtledreaming was since I wasn't around for it; things very catered to each character will obviously be extremely difficult to generalize, at which point the best option, in my opinion, is definitely to limit participation.