That in theory could have worked, that someone invited them, but as long as a god is still asleep, they are 100% human. Even the threat they're facing can't find them even though they are looking everywhere for 25 years.
So, the alternative idea: what if there was a concert, or a festival, and it just so happens to be that these characters are all here to enjoy the show, be it willingly, or forced by other friends.
And for the ones that traveled there a long way, maybe they made it into a vacation as well.
Of course having everyone on a vacation works too, just not that it's organized to bring the reborn gods together.
As for the banners, well then I might actually look into it :)