I agree with the "loose and easy".
Here in Taffmog we have several such days, organised by text/phonecall.
Not as a formal event which reduces MSA certs etc where needed!
Some are just a day run, others full blown weekend stays.
The more formal they are the more organisation needed, making the task more committed.
Weekends are the obvious targets so there are likely to be clashes but nothing to worry about as each will decide their attendance.
Again, thanks to SteveT for starting the ball rolling, I have missed those done so far but intend coming at the first opportunity.