Yes, yes, I realize that it's actually been in the vernacular much longer than Ginormous, and if you break it down into its component words it already exists in the dictionary as it stands today. But this isn't about the dictionary. This is about grammar.
As we all know, a group of geese is a gaggle, a group of crows is a murder, and a group of lions is a pride.
My proposal today would make the proper word for a group of Douchebags as follows:
A festival of Douchebags.
Or, in the more active form:
A festival of Douchebaggery.
Which could then be contracted to Douche'fest.
Unless you're talking about the actual objects, then the proper format would be:
A shower of douche bags, or a flood of douche bagging.
And here endeth the lesson.
It's a FESTIVAL, man.