Peter, We can use daughter's US UK-registered SUV for local use in UK. Then three options emerged considering 4 adult passengers: 1. all 4 fly in from UK/Stanstead to SoNL/Eindoven, and use yellow 73 Giulia for 2-3 week trip and fly back to Stanstead, depart from UK, 2. use daughter's US UK-regisered SUV and drive chunnel and back, 3. Rent a Stelvio or Giulia. The concern is 3x55-60 kg and 1x95 kg persons plus minimal luggage only in a Giulia for 2-3 weeks. Fred knows the drill here having done two US driving trips with 4x people.
Yes, I understand.
While you are in planning mode, you are probably aware that you can easily also do the Harwich-Hook of Holland ferry from your daughter's base (using the A14 highway down to Ipswich - probably 45 miles away), if you are planning on visiting Holland and save several hundred miles of detour through France and Belgium.
I know it's probably heresy to a 105 devotee, but I'm tempted to loan you my 156 GTA - 3.2 litres of V6 Busso goodness, a Selespeed gearbox and functioning aircon all included. All you need is your own oil well! That would make for a civilised summer road trip but while it would meet the passenger requirements in that it would seat 4 adults comfortably, I don't think the trunk would be up to the luggage required. The other problem is that the steering wheel is on the proper side
I hate to think what you would spend hiring a Stelvio or a decent spec Giulia for three weeks, especially with a full excess protection.
If your daughter's SUV is a left-hooker (and, after your experience last summer, the aircon works!), wouldn't that be ideal for four plus baggage on a European road trip? In your shoes, I'd probably just wince and spend the money saved on rental on fuel and an AA European Recovery plan. I know it's not an old Alfa but nor is the Stelvio.
FWIW, I have regularly driven a petrol Range Rover (4.4l V8) from the UK to Italy and back and it would return 15 MPG on cruise control at 130 kph on French autoroutes - the single figure MPG figure only kicks in above 100mph, where its lack of aerodynamic prowess really shows, but you can only do that in Germany (and I only do it there because I can, not because it's fun - my version of exercising my Second Amendment rights
A thought to avoid an Alfa drought: depending on where in France you are planning on going, you might be able to break away for a day and https://www.hameaudesbaux.co/convertible/
or Alfa Romeo Spider Giulia - Rent A Classic Car - The classic cars rental on the French Riviera
or Riviera Classic Cars- Classic Cars for Hire on the French Riviera