Should i go on vacation with my family or stay with my grandparents and work?

This sounds crazy when I ask it like that, but I'll be 16 next month and I really don't want to miss work which means a couple hundred dollars that could have been earned, all down the drain. I'm employed for my grandparents and they are hard-a$$es, so they are kind of pissed that I will be gone.. The only reason I am considering not going is because I really want a car, whcih i have to pay for myself, a laptop, and back to school clothing. if i were to go on vacation, i would miss the money. My parents and brother are going on vacation to cali, but they are going to the part that will be overcast and 70 ish the whole time..so i'm really not missing much. I do want to go, bad, because it is my vacation, but it just seems more logical to stay with my grandparents and work. I asked if i could work overtime and make it up but the buisness doesn't really work like that,it comes in steadily. Also, another lady that works there will be gone the same week as i am so not only were my grandparents even more ticked but its a lot of work to make up when i get back, and way more pressure if i do go. I just don't know what to do becaue I love vacations but it just seems like a hastle to go! :(