Wheaten Terriers tend to be playful, energetic, and fun dogs that are affectionate with their families. They get along well with children and other dogs. But, they have a high prey drive, so they will need socialization with smaller pets in the family. They also tend to be initially wary of strangers, but will warm up quickly once introduced if they have been properly socialized.
If the other parent breed tends to have a similar temperament, then you should be able to expect the same in a Wheaten Terrier Mix. You can also meet the mother in-person to see what her temperament is like and what kind of behavior she is modeling for her puppies. The breeder should have started training and socialization. But, once you get a puppy home, it is up to you to continue training and socializing them throughout their life.