Awesomesauce! I can't wait to get to write with both characters! My first thought was that Serena and Dan should find each other at The Palace (he's with Nate and she's with Chuck/Blair, right?). Because I imagine that's her current concern since she knows B, N, C and C are safe. Plus their date got royally destroyed.
And Serena and Carter will definitely need to thread and discuss their great escape!