Apple TV 4K via Beamer Watch Offline Movies?

I have the following problem. I own an iMac and an Apple TV 4k at home. Now we have a big birthday party to celebrate, so no way to connect the Apple TV to the Internet. Is there a way because, for example, AppleTV a self-made slideshow (imovie) on the projector (hdmi-capable) to run? Can you bring movies offline on apple tv? Or am I forced to organize a ps4 or laptop with hdmi?

Unfortunately, it is not possible to download movies, music or photos on Apple TV. You are always dependent on the internet. I think that's stupid, because you can also use movies on the iPad offline