It can be a fine line. Yes, the program appreciates saving money, and to that effect I don't offer accommodations to applicants from our home program since they live here and know their way around. If your relatives are close by and staying in their home won't interfere with your full participation in the interview activities, I can't imagine the program will mind. However, don't give the program the impression that you're just using the interview as an excuse to visit your relatives.
This is an example of what not to do: Last year I had an applicant accept the interview but decline the accommodations because she was going to stay with her aunt and uncle. She didn't attend the dinner the night before because she didn't want to disrupt their evening. She didn't come to Grand Rounds on her interview day because she didn't want to ask them to get up early. She did make it for her interviews, but our residents don't have as much time to talk during lunch as they have at the pre-interview dinner, so none gave me any feedback about her. The Selection Committee felt that her actions indicated that she wasn't serious about our program, and she ended up on the low end of our rank list.