They look like imitation pearls to me. They are very uniform, the drill holes are large necessitating large knots, and there seems to be some excess pearly coating near some of the drill holes, which one may see in imitation pearls. The bead tips where the thread meets the clasp is also a lower end finish.
Of course inherited pearls can be very sentimental despite being imitation. If you want to wear them, I suggest giving them a bath in some warm soapy water, wipe the grime off with a soft cloth, rinse them and let them dry on a clean towel. You can save money by restringing them yourself--it is not hard. You can find my tutorial and some videos on the Lowly Beaders' Club forum.