For creating a large banner for a charity event, Photoshop would be the best choice among the options provided. Photoshop excels in handling large images, graphics, and is capable of professional-level editing and design, making it ideal for creating visually appealing banners.
However, if the banner includes a lot of text and is more layout-focused, InDesign could also be a suitable option, but typically for pure graphic design work, Photoshop is recommended.