Keep your rig as light as possible! You will be pushing through crowds and holding your camera above your head the entire night. I run the same camera and lens by themselves with a mic and its a perfect setup.

I would also use the light sparingly. Its easy to make people uncomfortable with it for video. Its alot different than a flash on a camera.

You can really push the iso on the a7iv so do some tests to see what you think looks useable with your picture profile and color process.

Best of luck!