I think we miss a HUGE factor in this discussion, and it is very important to get it out there.
How you present your magic will probably be the cause if someone tries to ruin it or not. And I also believe it is not as much as ruin as it is "trying to catch you out".
If you present your magic as something impossible, that they wont believe theyr eyes, of course they will try to disprove that, that is how we humans work.
And I dont believe we can blame it for being a "family member" either. Sure they might be a bit ruder than average people on the street, if you will, but the truth is that there exist alot of different personas out there aswell. Some will try to catch you out. Most of them will, actually.
If you present it as sleight of hand, or something more of bizarre, they will probably think it is more of a physical ability that you have rather than "magic".
Great example is that if you go up to a stranger on the street wanting to perform for them, you dont say: Hey let me show you magic.
You probably would go a little more in the line with: Hey can I show you something cool/weird/strange/that I just realized I can do. (all depending on what kind of magic you do)
This relaxes them, and gives it a more natural flow than trying to hit them hard with something super natural.
Dont try to prove magic to them, let it happen inside of theyr head.
By that I mean, dont tell them that you are doing something magical, do whatever you want to do, and let them be astonished and believe there is no other explanation than magic.. (even if that feeling only can exist for a few minutes, youve accomplished something big)