I don't think the term is offensive. At the same time, I hardly believe it is "an instant" kind of process. For the sake of the children, one would hope that the process of blending is rather slow and takes into consideration the time the kids need to feel like a family.
I've been in dsd's life since she was 7, I lived with her dad now for about 4-5 years (losing track here heh), and she's been living with us full time for almost a year, since she was fourteen. Nothing about this process seemed instant.
I'd say it took us about 6 years to find our dynamics where she would feel comfortable with my role in her life, and I would feel "okay, I DO fill in a parenting role in her life".
I don't know the angle the show will take, and how all involved in it will feel, so it's hard to argue for or against the show without actually seeing it. That being said, I have a general distrust for the "reality" of "reality tv".