that is similar to what we're doing. we're getting married on a beach in St. Thomas during a cruise and then we'll have a reception in our hometown a few weeks later. we haven't done up our invites yet but I've been playing around with the wording myself. one way I came up with is

Bride's Name & Groom's Name
will be married
in St. Thomas, USVI
on December 9, 2008

Please join us in celebration of our marriage
December 31, 2008
time

reception location, address, etc

and since we'll be out of town doing the cruise/wedding from Dec 6-13 and our reception is on NYE, about 3 weeks after the ceremony, and Christmas is in there as well... I figured we'd mail out the invites maybe like a week or two before we go on the cruise (maybe like right before or right after Thanksgiving).