I think it'll be an anticlimax. Caroline will just be watching the house, waiting for OP to go out, then running off to get her car. Though good luck trying to hide a whole car, Caroline.
Really OP should have installed penguin bollards last night, so that Caroline would definitely have to knock to be let out. If only there were some emergency mumsnet penguin bollard installation fund.
If Caroline IS a mumsnetter, what could she do to make the situation better? Move the car and leave a box of chocolates/wine on the doorstep?