It's not about needing to show others that you are grieving, nor about telling others how to deal with it.
It's more about letting the families that are affected know that others care. Personal grieving, and private sympathy is certainly still warranted, but I am sure that collective...
Is it possible to fill the first page of the big board with a single tribute/donation thread - and all other threads start on page two? A match day would have greatest impact and exposure.