Bonjour Alexandra,

You could say ‘allez, tous en voiture’ or ‘allez, tout le monde en voiture’ although it does sound quite familiar / colloquial.

On the subject of ‘voiture’, there is a famous sentence in French: ‘En voiture, Simone !’ Here is an explanation to its origin, supposedly: en-voiture-simone

I hope this is helpful.

Bonne journée !