You're going on this trip, and there's nothing they can do about it. When they start screaming it's because they raise the level of energy in the conversation. This is a technique used by many to get their way. The best way to retaliate to this is to not let the energy level of your voice raise to their level. That's their field, and they will win.
Keep calm, and explain why you want to go. By keeping calm they might get even more frustrated in an attempt to shake you up, but keep calm. Let them finish their sentences, and when they have nothing more to say... if it feels natural to reply, you do, if not, just say that you understand they are worried but you have made your choice.
Over time they will hopefully accept that you've grown up:)