Is 18 years old too old to go on vacation with my parents?

my parents r going 2 this very luxurious hotel this summer for a few days and id like to go with them. i would obv not spend all my time there with them and i could go in the shopping centres and nightclubs and all, but i dont want to take any friends with me because it would make me uncomfortable, especially in the 5 hour car ride to talk with my friend and my parents r in the car too~~ so it would be me and my parents. is it innpaorpriate?