My advice is keep what you currently have. Buy a good video head tripod/monopod, a mic and lavalier mics, a cheap drone, and some video lights. A gimbal if you want to go all out.
That should cover all your bases at first. If you need to upgrade your cameras go from there. I think soon Canon will be forced to have Full Frame 4k in their morrorless bodies by competition so I would not buy a high end body from them right now. If you want to get a cheap video oriented body for your lenses as a stopgap I would go for the new 90D.
EDIT: Also make sure your computer and storage are good enough to edit and store everything!
Govind Vijayakumar got a reaction from BenEricson in Best event shooting camera + lens