Actually, the worst part about performing to your family is having douche bags in your family. My uncle (who is a complete and utter piece of trash) brought his whole extended family to stop over at my family's tiny town house for a week. I lent him my room, and lo and behold, he somehow found all of my gimmicks, even though I asked him not to mess with my stuff. Later in the day, I performed one of my favorite tricks for them. He leaves, and comes back with the gimmick I used, and asks me if I used it. I tell him yes, then ask him not to tell anyone about it. He says okay, only to go show everyone he knows.
That experience taught me 3 things;
A: Never perform for those who don't actually want to be entertained. If someone wants to just mess with you, say no.
B: Never rely to heavily on one trick. The trick I used was one that I had used extensively. However, upon my uncle revealing it, I started to try and find new ways to perform the same trick that would leave me clean. I also learned to organize my routine.
C: Always have an escape plan. Never allow a Heckler the opportunity to mess with your cards. Either shuffle and cut the cards, or give them a pass, palm off the gimmick, or whatever you need to do. Just make sure you don't leave yourself open.