I like the idea that we're a newly formed group of well-respected heroes that don't know each other personally. So Steve and Hyp, since you're both the Leadership folks, how about you two sat down one day and decided to set up a do-gooders organization, combining your command infrastructures? Then you set out invitations to hero/adventurers such as ourselves to join you with the esteemed goal of spreading right and good.
Here's a spin that I, personally, would love: It's a clandestine organization. While we are all respectable individuals, we're in Forgotten Realms and we're not epic level. Therefore, we are not legends. We are known only in certain circles. The "Some name involving shields" is a secret, because to be high-profile would mean the Bad Guys (tm) would know about us, and so factor us into their plans. Being secretive gives us the element of surprise.
So this night of partying may be the Grey Shields/Shields of Shadow/whatever at only a week old.
This also brings up the question of funding. It could be that the regular folks, the followers from Leadership, are really just informants and minor servants. They have their day jobs, but have connections with "the Good Guy Mob." As for us Boardmembers, their are two routes:
1. Certain Waterdeep officials, lords, and whatnot know about us. This night is the first night we've actually been employed, however covertly. Peregion hired us for protection, and Aleena doesn't even know we're guarding her. So we have the drive to not screw this up, as we don't want our first customer review to be a bad one.
2. We do things out of the kindness of our hearts, and earn cash the normal adventuring way: Kill baddies and take their stuff

So both Peregion and Aleena don't what we're doing.
Either way works for me. I just would like the PCs to still be very unfamiliar with each other, so we have room for character interaction and development.