I'd recommend installing a NEMA 14-50R receptacle in the garage and then buying whatever EVSE ("charger") you want. That will set your house up for the current standard of supplying electricity to the charger.
The 2016 Smart has "only" a 3.3kW charger built into the car, so you can buy any EVSE that can deliver 15Amps at 240V and the limitation will then be the charger built into the car rather than the EVSE on the wall.
Charger: Electronics built into the car by the factory.
EVSE: Electric Vehicle Service Equipment: Thing that plugs into the wall (or is hardwired) and has the plug that plugs into the electric car. Most everyone who is not experienced with electric cars would call this thing a "charger", but the electric vehicle engineers decided not to adopt that language, unfortunately.
14-50R: A specific type of wall receptacle ("outlet") that can supply 240V AC at 50 Amps. Your EVSE will plug into this.
Here's one randomly selected example from Amazon: https://www.amazon.com/Zencar-100-24.../dp/B07J56WF9K
I have no specific experience with that and would probably be more inclined to buy a Clipper Creek unit myself, but the unit linked above will work for Level 2 charging your son's car and is fairly inexpensive.
The protocol for the charging is such that the high power electricity is only "live" after the car and EVSE negotiate a connection, so there isn't much worry about the cord being out in the weather, about plugging/unplugging when it's raining, etc.