Isofix

[Enoch]

My recommendation would be a Lamborghini LM002. You get lots of miles to a tank of fuel but that may be because they have 90 gallon tanks. Or something.
Ideal from a safety point of view. Tyres are a bit dear though.
Same engine as a Countach, very tuneable, perfect for doing the shopping as they have a very large boot. You can always find a parking space, other vehicles being in the way cease to be an issue.
You will never lose it in a car park, especially if you paint it bright green / pink / yellow or whatever.
I am sure that they have isofix but can't guarantee anything other than sub 10mpg fuel consumption.
Hope that helps.