Last I checked you have to be 21 to rent a hotel room? And a rental car...
I did something similar. Nothing happened between us, I was very cautious and whatnot.. but the difference is I payed for everything...ticket AND room.
I think that's the main difference. If he buys it, his name is on there and technically you are HIS guest. If you buy it, your name is on there and you can kick him out if need be.
I live with my parents and I contribute to paying for food and gas and stuff. I pay for all of my "luxaries" myself. But I'm also very smart in having 5 backup plans incase things go bad with my guest.
You may have dated for 4 years but that doesn't mean you can just completely let your hair down. You're still young...he's probably still young. Your parents are right to worry.
If you can't afford ticket and hotel then you shouldn't even go IMOP. Just wait, and if your bf can't wait then that says something about him.
Sorry, I went there.
"Strength is the ability to use a muscle without tension"