7 or 7+? Both have optical image stabilization, but the + also has optical zoom @ 2x.
Since i'm not set up for 4K i use 1080P, but if i ever want to keep a video for the future i'm using 4K. I tried some video, and photo's inside, but the light alway's throw's off the color. I did take pic's while walking in the park. One normal, and the second of the same subject, with the zoom. I was very impressed for the first time using an iPhone camera. Then i took a video using 1080P, and 4k. I used the zoom for both, off and on, off and on. When i played them back i was really impressed with the zoom feature.
Kid's are fun to photograph, because they have so many expression's. Before this 7+ i alway's used my Canon EOS 20D for photography, because like i said i've never been impressed with the camera on iPhone's. Now i'm thinking i don't need to use the canon?
Technology change's monthly these day's, so i would say if your keeping your video's use 4K. Take the kid's out side on a sunny day before winter come's and the color's change. You will like the video's even more, because the color jumps out when it's natural light. Shoot some in the sun light, and some in the shadow's of something like under a tree. If you have the 7+ practice with the zoom. That way you don't have to be so close to them, and kid's can do, and say some funny thing's when their in their own little world.