If you want to keep using your canon L lenses then the A7sII makes more sense.
In therms of all in one camera I like the sony X70, great battery life (8hour), 4k, nice low light, extremely good stabilisation. It's the one I would probably use for a trip like this. If you want a camera that does both still and video the gh5/gh4 is probably the best choice.
Imovie only allow for a very basic edit but cannot provide a professional result. One exemple of how limited it is, is that you cannot do any audio crossfade between shot. If you aim to make a familly film it's fine, if you want to reach a larger circle you need something better.
I would advise to go for final cut pro X as it is easy and cheap and there is almost no limitation in what you can do as solo editor compare to other pro editing software.
For me the most interesting camera is the c200 as it has the best versatility, it can do great run and gun images with a reliable autofocus for small daily job and be also used to shoot raw on high end projects. I do like the fs5 too but the canon c200 is just better in every area, all I miss now is a good affordable 17-110 all in one lense for those little jobs.
Fyi most of those tricks can be easily replicate and better controled into photoshop, but for amateur it can be a good way to have fun with your camera.
If you want to go the canon way then go dirt cheap on the body as the newer models don't have a significantly better image quality, get a used 600d, eos M or something like this. Download and instal magic lantern on it and use the vision color picture style. Then with the money left get good lenses with fast aperture, a tripod with fluid head and a good shotgun mic with +20db feature like the takstar or the rode videomic pro if you can afford it.
I shot this with a 600d and an eos M and it looks totally fine to me. https://www.youtube.com/watch?v=QB8RsA-AAo4
That said if you can afford it I advise you to get something better strait than a canon dslr, the panasonic G7 is great, the sony a6300 too, both are very cheap for what they offer.