I'd just assume it needs to be rescheduled into 2021. Should group gatherings resume before the end of the year, which seems unlikely, it seems a safe bet that turnout would be rather low just due to people not wanting to risk it. On top of that, we're most likely going to be neck-deep in a pretty painful recession (at least) by then.

It's probably not a good idea to hold such events before a vaccine or an effective treatment are available. Neither is likely in the next 12 months.