In this case there will surely be a "clearance" for the night operations to be performed and all affected personnel will be able to grant the service. I'm not sure about the duration and altitude of your flight, and also distance from the cleared airport, but I'd suggest you provide yourself an alternative way to contact ATS units (apart from VHF) to inform them on Operations Normal (every 30'), as radio coverage over the sea and in mountainous areas tend to be bad or worse, if you are close to the surface. Or even ask for the phone number of the unit/center under which you will operate. All this, unless you will be in constant contact with an "operations center" that can rely your ON to the ATS units, to avoid any alerting phase being activated...
Have fun and hear you soon