Good point about Avios earned etc but I'm guessing she won't know or pick up on the significance.
Thanks for the nod about Avis/Budget - I always select Avis as I'm Preferred and I like the service.
I'm on a redemption so can't switch names, and the accommodation is already sorted so don't want to book hotel nights, and we do need the car anyway.
I've realised that I have switched lead driver at the desk before now (renter lost their licence in transit) and it was no problem but I don't know if we got lucky or its a pretty standard thing.