@johnw1984 hoping this won’t be a classic case of answering a different question but do you/your wife actually need a Gimbal?
I take a lot of GoPro footage and have edited them into numerous movies. With a bit of practice you can shoot perfectly usable footage without a Gimbal.
I tend to edit my footage into pop-style movies with many scene changes and short, maximum 20 second segments of footage. If I’ve shot any footage that is a bit wobbly that just gets dropped on the virtual cutting room floor and I use some different footage instead.
The chesty mount is pretty good for decent footage. The secret is to have the straps as tight as possible. Also I found that my original GoPro Hero (GoPro 1 if you like) that i bought way back in 2010 was fairly bulky and tended to bounce around a lot more than my GoPro Session 4 which is much lighter and therefore less likely to move on a rough descent.
So in short, get out there, shoot loads of footage and play with the editing to gain experience. You soon learn what makes a good shot and what doesn’t as well as what the limitations of a GoPro are.