Holiday Autos is just an internet clearing house for car hire. You will probably end up getting the car from Europcar or somebody.
As advised, go for the Swiss side at Geneva because the French territory exit is fiendishly complicated and returning depends on finding a little-known sliproad at the border.
When you return your car, first drop your passengers and the baggage at the terminal. Then refill your tank at a small Elf filling station underneath the World Trade Centre, on the right as you approach the car hire return. You have to insert a payment card in one of the payment posts, nominate a pump, fill up, then go back and re-insert the same card for a receipt. It’s a horrible system to use when you’re a bit stressed so leave lots more time than you think you’ll need. From the car hire place there’s a shuttle back to the terminals.
