How far is it from where the Hoverspeed docks at Calais to Hertz rental at Calais Eurotunnel at 1450 Boulevard Du Kent? Can it be walked with luggage or will a cab be required? Is there a ATM at either or both places to get Euros for the cab?

The last time I was at Calais, we dropped a Hertz rental car at the Hoverspeed Docks! You may want to ask if this is still the case.

It's a looong way, something like 6-7 miles. Hoverport is to the east of Calais Port, and is connected to Calais-Ville (downtown) by a free bus. Eurotunnel Terminal is south-west of Calais, off A16 autoroute at exit 13. There is a bus (No 7) that goes from Calais to Cite Europe shopping mall, which adjoins the terminal. A taxi will be possible, maybe 20-30 euro?
If possible, it will be easier picking your car up at Calais downturn location in Place d'Armes.

Maira is right. Hertz does have an office at Hoverport.
See http://www.hertz-grand-ouest.com/adr...s_hertz/62.htm

The ferry terminal has ATMs and has (or at least had) a Hertz counter. It might pay to phone from Dover with your arrival time, as we had a fairly long wait for someone to come from one of the other offices when we picked up a car there.