You should focus on one aspect and make it available in slightly augmented form in the other phases, too - or simply think about whether you really need those two parts
The problem is that you are proposing two very different approaches. Rushing through everything with brute force can be great fun and many people like it. But it's very different from what you expect when you want to play a horror game with a mostly helpless protagonist, like a little child. It doesn't mix well, because you feel like you are thrown into parts that are just not what you want to play.
You should think about making your story contain action on both sides or on neither side. For example you could let the child "fight" someone or something, too. But it's far smaller and ideally a different kind of threat. Instead of simply saying that the child has to find a weapon to fight of one person in a camp you could center your story around the kid fighting other kids/animals/... for food while sneaking around and the two martial artists fight against multiple enemies, because they are simply not that good at sneaking around.
Or you could think about making the martial artists be able to fight off more enemies, but encounter more enemies anyway. That way the power-level in relation to the rest of the world would be equal.
If you don't do this your main protagonist will feel pretty useless. After all, the martial artists are better. In everything. According to your description the child can't really do anything and has to find difficult ways around, while the other guys simply rush through all the trouble. It's the same thing again, just easier and less scary. Why would you want to play that?
It's perfectly fine to mix the point of view of characters who prefer the direct approach with the point of view of characters who prefer the subtle approach. But making your reader/player/... go through the subtle part, only to immediately afterwards be reminded that thinking isn't really necessary if you can just bash your way through is bad.
Ideally your characters would face difficulties geared towards their strengths and weaknesses and they wouldn't interact with each other. This way you can change the pace a bit and still provide a similar feeling of dread. Or you could have to make your characters influence each other. Have the kid sneak through and the guards detect that someone stole a few keys - everyone in the camp is on edge and now it's harder for the non-sneaky guys.
Think about your target audience: do you want a horror story or an action story or a mixture? What you currently have is neither - it's a story that forces one side of these people through parts they probably don't want.