It may be an option to call the police to tell them about the cruise, but the problem is not all the police get informed or the msg doesnt get out there and hence being infective in the first place
Also they may take it upon themselves to decide to easily locate and defect us while where there
its a 50 50 chance situation
you either inform them and run the risk of telling them "hey..defect us"
or eliminating any problems with them
personally, i say dont worry about informing them and just liason with them on the day
we did that with the jap cruise (and that was over 150cars) and we had one serious hitch in which only (i belive) 2 cars got defected that night
but it was my fault for even having a meet spot at such an open and publicly seen area
another thing is, seeing as this is a day cruise, police generally dont think we going to have drags or run amock during the day
they have the thought of: lots of cars + night = runs/skids
think most clubs have had minimal interference with police on day cruises
its the sad truth, but not much can be done