is it stupid to save up alot of money for an expensive trip once?

is it stupid to save up a lot of money for an expensive trip once? my dad says it is stupid of me to save up a lot of my money just for a trip to disney world i want to go with my grandma. he thinks on my salary i should not be thinking about vacations I should rather pay off all my college debt. I think that since my grandma wont be around as long as im paying off so much debt i should do things with her in the near future. im not sure if it is going to end up that my dad is right i should not say up for such expensive trips, i would really regret it if i bought my grandma and me a ticket and she dies after i buy it for her ,I would really regret it, she is close to 75.