Help My Parents Get Out of Debt

So as most of you probably know, in college you have the options to use student loans to pay for stuff (I haven't gone, so I don't know very much about them). And my parents used these and still, after 15 years, they still have not been able to pay it off. So I have decided to surprise them for Parent's Day (it's a holiday that my family does. we basically combine Mother's Day and Father's Day.) and raise money to pay off their student loans debt. I believe my parents would love this; they wouldn't have to worry about paying off debt, so we could focus on finishing our house (we're in the middle of a remodel) and fun activities for the 6-kid family.