Help with my sisters propsal

Hey girlies! So i need help planning my best friends proposal any tips would be so appreciated!! Its 3 weeks away and so far me and her boyfriend have come up with the general vibe that he wants me to execute lol. He's a shy guy so it wont be anywhere public, right now we're trying to figure out where to do it at that'll be private just them two but still giving her the grand proposal of her dreams. I don't want to give too much away incase she might see this because she is on here as well lol. We are going to do it in Minneapolis a little ways away from home but she loves the city so trying to do it there. Please give me any advice even if it seems off topic!🩷