Thanks to everyone who co tributed here so far, very useful thread.

My wife and I have a 16 day holiday coming up in the 2nd half of March and there will be a lot of driving. We arrive into LAX, pick up the car and do a big tour via Las Vegas, Salt Lake City, Lake Tagoe, San Francisco and then to San Jose from where we’ll be flying back home.

I currently have a Mustang converible reserved (did that a while ago so relatively reasonable priced) and am now considering changing it to something more comfortable due to the long distances we’ll be driving, the fact that my wife will be in the 2nd trimester of her pregnancy and that we’ll probably also have a bit more luggage. Was thinking to get any of the Mercedes’ currently on offer (GLA, C class, E class, GLC) because of more comfort and space.
I got the Platinum status a couple of months ago via actually renting cars so should be eligible for the double upgrade...

A hypothetical question - S class and other X... vehicles are currently shown as sold out for our dates - would there then simply be no upgrade or would they go above and beyond if I would book an E class now?

Any views are greatly appreciated!