Arrange the surprise Bday-party for my sister

I have a sister whose name is Liza and she will be 25 soon. I love her very much and I want to arrange a surprise party for her. I know she like surprises, as well as cheerful parties, big companies and so on. So what we have? Liza’s Bday is in 3 weeks. Do you think it’s enough to arrange a nice party? I think I can do it. I prefer to do everything in advance so I’ll try to arrange it very fast. As a character from my favorite series says, Challenge Accepted!