Their interactions will require constant supervision. Even good hearted play can lead to serious injury due to size and strength differences. Im not against letting my dogs sort out "some" of their own problems, but ultimately it's the humans that need to be setting the ground rules. Your GSD may be very tolerant of your bichons interactions/corrections now, but that can change down the road and one slip up can end badly. Watch their interactions and intervene before your bichon feels the need to correct the pup. Doing so can curb potential problems from escalating, set boundaries for the pup, and (with consistency) let the others know you got things handled.Keep in mind the temperament of your GSD will play large in all of this and your breeder "may" be of some help determining what to expect.