I love the binary numbers bit. It appears very often in sci-fi when interacting with aliens. very good to have it explained nicely and be a "puzzle" to solve.
But I'll just note that as far as I know - von Neumann probes are not passengers, but rather the ship itself, which replicates and travels to new destinations.
It might be ok in this short story because kids found the ship, so they didn't know better, but it's important to get the science right in sci-fi. Readers are smart :)
Keep at it! I'd love to read more of your stories. (Short stories are great for sci-fi in my opinion!)
P.S
A great book about Von Neuman probes is - We Are Legion (We Are Bob) by Dennis E. Taylor