I would
head into Rodney Bay Marina to clear in, that is much better than Soufrière. You can
anchor outside and
dinghy into the marina or go into the marina.
I doubt that any office will be open, but in Rodney Bay they will open up (for an out-of-hours fee). You can e-mail the Rodney Bay marina and ask them about the
customs & immigration hours for New Year's; the office is right next theirs and they are quite friendly there. My
boat is currently in
storage in Rodney Bay and I hope to be back aboard for New Year's - I might even be anchored out that night!
Are you coming from the north or the south? Soufrière is much further south and perhaps better suited if you are coming from there. But I think Rodney Bay is better protected and you can
anchor in quite close in good holding while Soufrière is not as amenable.