For just puttering around town @ 50 MPH or less, both the model 3 and Y will give you 3 miles / Kwh, easy.
One thing to remember when charging a Tesla on a welder or dryer outlet, or even the dedicated wall charger; you do not need to use the full output of the outlet. Whether you use the phone app or the screen in the car, you can set the max charging rate. A 240V outlet charging at 22 Amps will give you 5Kwh, which will get you 15 miles of added range every hour spent charging. Two hours per car, will get you 30 miles of range. If you bump the charging rate up to 44 Amps, you will see 60 miles in two hours and still have a bit of safety capacity on a 50 Amp outlet.