Hi, "group";
A Halon 1201 or 1306 extinguisher using an appropriate-sized bottle (ask your rules organization) would be appropriate. The water-foam extinguishers are not something I'd use around an electric propulsion system.
You will probably want a couple of nozzles placed around the battery pack, one or two covering the controller, and one or two in the driver's cockpit. Check the rules.
Have fun, be safe, go fast.
Regards, Neil Tucson, AZ B/GMS