Tell me a scary story, but not one that's so scary I can't go to the bathroom in the middle of the night.
この場合、次のような言い方ができますよ。
ーTell me a scary story, but not one that's so scary I can't go to the bathroom in the middle of the night.
「怖い話をして。でも夜中にトイレに行けなくなるほど怖いのではないやつね」
a scary story で「怖い話」
to go to the bathroom「トイレに行く」
in the middle of the night「夜中に」
ご参考まで!