well this might not worry some people, but I wouldn't have anyone else there anyway in case it turned out that it was an internal ultrasound, to me I don't want an audience for that sort of thing.

My sister had her MIL to her scan with her DD and it turned out she had problems with placenta previa and she said it was awful having her MIL in there getting worried as well, so I would stick with the "it's a medical procedure" line just in case.

All the best.