Remember that you will need some drop distance. This is the distance that the cord has to come up from the ground to the outlet, and you loose about 4 to 5 feet due to drop length depending on where the charger is. For example, ChargePoint is at the rear of the driveway on a post and while the cord is 25 feet, long, I have about 3 feet of drop (from the charger, mounted on a post about 36 inches from the ground, to the and the couple of feet that it drops from the car end to the ground. This means that I really only have about 20 feet of cable that I can use.
The Honda Emergency Charger will have some drop from the outlet to the brick, but the major drop will be about 2.5 feet from the socket on the car to the ground so a 16 foot cable really is only about 13.5 feet in practice.
Don't forget to calculate this in if you ever install a 240v charger. It could mean the difference between being able to reach the socket and not being able to reach the socket.
12 gauge wire would be best but 14 will probably be OK but only if it is a shorter length (25 feet maybe) Just feel the extension cable and the extension socket when the car is charging and if it feels hot to the touch, you might consider a bigger gauge extension.