Too weak when it comes to my Parents

I'm an only child. All the pressures on me. My parents are the best. Still, there are times that they are not perfect. Just like me, I'm actually worse. I'm stubborn and do crazy stuff but never spoiled.
I'm curently in LAX. Going out of the country for a week. This was planned not even three weeks ago. For rich people, this might not be a big deal but for a 21 year old who works as a part time that still live with her parents, it is. 
I don't tell my parents everything. They're not my best friends but my parents. We tell each other stories of everyday lives but I never get personal with them. 
I got so many days to tell them face to face about this trip, but I didn't really plan on it because I don't want to see their faces being so disappointed or embarrassed by me. Weeks go by and I just told myself I'll text them before I drive to the airport. Thats what I did today. Mama said why didn't I tell her last night when I got home and I said I was shy. My father called me thrice, and I didn't answer because I don't know what to tell him. I don't want to hear his voice where he might say what the hell am I doing. My mom would say why am I wasting money.

Thing is, I'm the one being so paranoid of what they might think. I cant force myself to tell them directly or else I'll run to avoid the conversation. Those scenarios can be true but I don't like the fact that I don't have the guts to this to them. I'm the one who doesn't trust them to trust me. And I'm embarrassed. Embarrassed about me being so weak when it comes to them. I love them forever and they're my mama and papa. 
I keep telling myself that I'm brave and courageous but when it comes to my parents, I'm such a baby. Well, I'm there baby, lol. Still, I don't know if I should change this about myself. Perks of being an only child. Good Luck to me when I get home. Especially the look on the face of my father.

All my medical checkups have been rescheduled by me and work is all good. It's just a week anyway and I fixed everything first before I jump into this madness. I paid for everything and they didn't even have to worry about me since I got everything under control. Well, they will worry because I'm their daughter. I hope they'll think of this time as their vacation from me. 
I'm sorry mama and papa for this sudden trip and the part where I told this to you guys on the day of my departure. I know you'll understand and I love you.