I understand your urge to educate your cousins in how awesome snakes are. However, I hope you think twice about forcing it on them at a fish fry. If they are so afraid that they unfriended you on FB, then they may have a real phobia and exposing them to a surprise snake show at the fish fry, may just make it worse. Not to mention, create more hostility in the family.
I have family members who do not like snakes. The way to convince them is to allow them to become accustomed to them on their terms. When these people come to my home, they don't even see a snake, unless they ask. If they are comfortable with seeing them, I take them to the ball room (what I call my snake room). I will pull out a small very pretty one, like a pied or spied and handle it so they can see it. Then maybe go to a larger adult. I will hold the head and allow them to touch the tail, if they want to. Many people like the feel of the bellies.
The whole time I'm doing this, I talk about how cool they are and how they are cared for. Normally, before they leave they not only hold one, but seriously think of owning one. Bring people along at their pace. Sometimes it takes two, three or four times visiting the ball room before they will touch or hold one.
Of course, some of my phobic family have still not seen them and that is OK. We progress their education at their pace, not mine. It is your job as a snake owner to make sure your snakes and guests are comfortable and safe.