I'm shooting video for my uncles wedding in two days and only have recently began understanding the relationship between frame rate and shutter speed for shooting videos (I have only shot travel films and personal stuff for youtube before, so I'm feeling the pressure now for Saturday.)

To get nice smooth slow mo on my 5Dmii I'll be shooting 60fps at 720p, but I'll be doing it all hand held so it won't be the most stable thing in the world. What shutter speed should I be going for to make it as smooth and with at least shake and blur as possible? 1/120? or less? Any response asap would be great.

edit: I'm sorry IDK how to add a flair on mobile

edit: My biggest issue is obviously not wanting choppy footage in slow mo. Also if I'm shooting both slow mo and normal speed parts should I be switching between 30fps and 60fps when recording? And then starting my fcpx project at 30fps?