Normally, it's advisable to not sit with a full 100% range charge for too long. I'd ask your delivery specialist in Tilburg wheter it will harm your batteries to have the car 100% full on the ferry for nearly a day.
My rule of thumb: When on a road trip, don't be afraid to do a range charge. I might need those extra kWh. But then again, I'll always use the car within max an hour after a full 100% range charge.
I've driven from Palermo to south-east Sicily and back a couple of times, though not yet with my Model S. Sure, the motorway to Catania, Siracusa and Avola will be faster, and the view of Etna is always nice. But taking off near Enna and then taking the country road past Piazza Armerina and Gela, and then maybe the road next to the sea through Santa Croce Camerina and Marina di Ragusa is quite nice, a bit shorter, though slower.
The uphill stretch of the A19 from Termini Imrese at sea level to Enna (elevation 900m) will probably be nerve-wrecking, as the energy meter in the Model S will probably predict a high kwH/km usage, and shorter and shorter range left for the car. You'll get some of that energy back on the downhill stretch after Enna.
One trick worth remembering is that marinas often have red 380V-400V three phase sockets, and they will often be happy to sell you some juice. The porto turistica at Licata or Marina di Ragusa might be of interest. Might be wise to call ahead to check if they can accomodate your car now in August and have an 16A 380V red socket available. If you only have the UMC and the red adapter, you will only get approx 50km of range per hour charge on a 16A 380V red socket. (If you have a 22kW portable wallbox you could have got 100km of range per hour on a 32A 380V red socket.)
Speeds higher than 80-100km will cost you some range. AC will also cost you range but is *essential* in Sicily in August, and rolling down the windows while driving will cost you more. You might want to put your car in range mode (will reduce power usage and effectiveness of your AC), and put the air suspension in low position, to save power.
You will be nervous when testing the range of a brand new car driving through places without much charging infrastructure. That's only natural. I took my Model S on a drive through Denmark on my first week, with wife and small kids, with headwind and rain, before there were superchargers or even 11kW chargers in most of Jylland. It makes for a good story now.
Also: Remember that the Model S is *wide*, and the streets of historic Sicilian towns can be *narrow*. Don't get any scratches from the careless Italian motorists.
