Personally I think MPG or L for an electric vehicle is meaningless and confusing, so I hope you don't do it that way
A gallon of fuel has a certain volume but the density of it changes with temperature, and the energy it contains varies according to the refinery processes and summer/winter blends, addition of biofuels, whether it's petrol or diesel or LPG, etc etc. So it's actually a pretty unprecise measure.
A kWh is a kWh, a precise, unvarying unit of energy. You'd actually be better off converting all the liquid fuel quantities into average kWh values (a litre of petrol is about somewhere around 11kWh IIRC).
Anyway, I don't see the issue with reporting kWh per mile - most EVs do between 0.2 and 0.5 (or 200 and 500Wh/mile)
Hope this helps.