Condensed version of my earlier post (plus extra bit!)…
If we always send our next postcard to the next numbered person on the list, and keep on going through the numbers, everyone should be getting postcards. If new people are added onto the end of the list, so long as they follow the same idea, with the last person on the list sending to number 1, everyone should keep getting postcards.
The random numbers system should work too - just sounds more complicated (I work with kids, so am used to not everyone having the same concept when counting on more than one forward or back!!! :] )
Once we’ve sent one by ‘the system’, there’s nothing to stop us sending extra postcards to people we just fancy posting one to. :