1) it's from 1-4pm, "open house" style, come and go as you please
2) not a wedding, they got married elsewhere and this is their "back home" reception
3) it's at a building in the park... enclosed, so not really a shelter, but sort of a shelter
4) facebook invites only, not a printed invitation
5) it's 40 degrees outside... not really a factor indoors I realize, but I'd still have to wear slacks for the way there if I don't decide to just really go casual.
*eta* - I just HATE cold weather, it makes it so hard to be in between casual and formal, who's with me?