OP I see two issues:
- Your immediate family members are afraid of your snakes and don't want to be around them; whether that fear is based in logic is a moot point. That's easily fixed, you leave your snakes home when visiting family, which makes both your snakes and your family happy. OTOH you will never have to worry about hosting family or holiday get-togethers as long as you have snakes in residence, which makes life much stressful on you.
- Your immediate family members also have dogs, you are allergic to dogs, and yet your family members bring their dogs to family events knowing that you will be there, or allow their dogs to come into contact with you. You have a legitimate health concern that they are ignoring, and you have every right to be PO'ed about them not showing you the same consideration that you show them. Since they won't change their behavior you can either choose to 1) put up with it, or 2) politely decline invitations to occasions where people will have their dogs with them.