First you need to understand some basics of discrimination law in your area. I can only speak to the United States generally (and will note some exceptions below).
In general, in the United States, antidiscrimination law came about because of the experience of segregation, and it attempts to balance the legitimate needs of businesses with the general interest in society of not having specific vulnerable groups targetted for problematic treatment. I think this same balance must exist everywhere that antidiscrimination law exists, but lines need not be drawn all in the same place (and indeed aren't even in the US). In the US for example, race is generally held to far stricter criteria than just about anything else because of our bad experiences in this area.
Consequently in most of the US (California state law aside, see below), the question of whether discrimination is illegal has to do with the reason for the discrimination and its impact across society. So for example if I give all African Americans a discount that would be illegal because this would be discriminating on the basis of race. If I give blue-eyed people a discount, the same would probably apply because blue eyes very strongly correlate with socially constructed racial categories. On the other hand if I give non-profit businesses a discount, there is no reason why this would be a problem. Similarly if I give family members a discount, I would expect even if they were all the same race that this would be ok, because family members are such a narrow slice of society there is no general social damage done. In general, with friends and family members, in the US, you aren't going to run into trouble. I do not know about a few exceptional places like California though so if you live there, a quick attorney consultation might be a good idea.
I single out California because that state has its own approach to anti-discrimination law which is in fact older than US federal antidiscrimination law. The Unruh Act is generally interpreted to ban discrimination in business dealings on any criteria outside the business deal context (I suspect that friend/family discounts would still be OK but I am not comfortable saying this for sure). The Unruh Act is sufficiently vague that even the ACLU has fallen afoul with this act for kicking off-duty police officers out of meetings on police surveillance.
I say generally interpreted because despite what the text of the law says, the California courts have generally looked to legislative history to see the law as advocating an end to any discrimination on non-relevant criteria. Again, California is an exception but it shows how far this can vary even within a single country.
So my advice would be to start by finding out what categories of discrimination are banned where you live. Chances are you will find that this is not an issue. However if you are still concerned, this is something an attorney should be able to clear up very quickly.