Tough call. As long as they don't go out there and try to do any WOT blasts around the corner. If they do, it would surely go really rich and could possibly wash down the cylinders. Anytime I've had alignment work done, they don't test drive the vehicle, the machines today are very good compaired to many years ago technology. I'd tell them specifically, do not test drive the car and that you have the mileage recorded. This would be just to cover yourself. If they insist on having to take it for a spin, I'd shop elsewhere.
HTH
Patrick