Humor is hit and miss, even if you have a gift in thinking of funny things to say and/or have a compelling delivery. First date is a time to stick with hits and then use whatever in-the-moment comedic gifts you have when the opportunity arises. Crafting a prepared line is for other times and situations. One other thing, about running, endorphins can make you think an inspiration while running is better than it will play out in real life,
Note that this board, on the whole, did not want to steal your line, but improve it. That’s her likely reaction, some version of oh, I wish you had said something else just then.
Part of humor is surprise to the listener. If you are saying something spontaneously, the freshness of it will be detectable in your voice, just as the staleness of the prepared version would be. I find it much easier to be funny when my ideas are fresh and partly a surprise to me. We laugh together. It also will encourage her to be freer and more spontaneous too, which is an actual first date enhancement,