Michelin Pro4 25mm with their A1 22-23mm latex tubes work very nicely in combo. I've not taken that combo to the alps but wouldn't hesitate. Don't drag the rear brake and any race tyre with those tubes will be ok.
Whatever tyre they go for maybe suggest having a spare tyre back at the hotel/HQ/megayacht. That way they can ride relatively uninterrupted rather than waiting for bike shops to open etc.
Michelin Pro4 25mm with their A1 22-23mm latex tubes work very nicely in combo. I've not taken that combo to the alps but wouldn't hesitate. Don't drag the rear brake and any race tyre with those tubes will be ok.
Whatever tyre they go for maybe suggest having a spare tyre back at the hotel/HQ/megayacht. That way they can ride relatively uninterrupted rather than waiting for bike shops to open etc.