I see. this is not the first time I came across such a request. there are several ways you could lock the content in a way that changing it will be problematic, but isn't the whole idea of giving source files is to allow changes to the file later on? anyways, let's try to get creative with this. there are two ways that come to mind:
1. pre-render some of your comps, so there will be much less keyframes, just mostly rendered footage item
2. bake your key-frames via an expression. click alt+stopwatch, and type value. now right click on the property, go to Animation - > Key Frame Assistant -> Convert expression to keyframes. the animation will of course remain the same, but to change it will be a headache because instead of this

you will get this
