My experience was similar to TD's, where we would have a few informal Summer picnics on Sundays after the meeting or field service (some years our meetings were on Saturdays) along with a game of softball if enough people showed up ready to play. These weren't set up via messages on the congregation message board (a literal, physical message board-- this was the 80s and 90s!), just word of mouth. As long as you had that one person who worked tirelessly to get things organized, it worked just fine.
They felt like 'congregation picnics' because it was only JWs attending, with possibly an interested friend/family member or active study brought along to see how much gosh-darned fun it was to be with Jehovah's people (ie, the only people who would not be gruesomely massacred in the soon-to-happen battle of Armageddon)!