how do i make a story based on diary entries still sound like good writing?
i’m making a scary story about kids who get trapped in a haunted house…
how do i make the diary entries of one of the kids still sound good.
(the whole story is the diary entries)

Pay close attention that you stick to a voice that is readable, yet believeable as being a child’s diary. Maybe you could try a frame structure that justifies the existence of the diary, like a testimony of someone who found the diary wrapped around the actual entries.
I’m not sure how to explain it…. Why don’t you take a look at the book The Princess Diaries? The whole book is basically her diary entries and while I was reading I would totally forget it was a diary until the date of the next entry. It was basically like a book from a first person p.o.v.
Even if you don’t like it or something, you don’t have to really READ it, just have a look at how it’s written.
Your story sounds interesting, btw. If you ever get it written and published or something, email me lol. Best of luck!