If you take a look at children's songs on YouTube you'll see that the majority of the videos in the top positions have a like to dislike ratio of 2 to 1. Sometimes it's even higher than that. The dislikes are from viewers who the videos aren't even targeting, likely teenagers. These videos are ranking in an extremely competitive niche where the average top position has at least a few million views. As
@Courtney Candice says, YouTube likely sees the dislikes as an interaction. Although they may prevent a potential viewer from watching the video (very unlikely), the dislikes won't affect the ranking (at least in a bad way). Some of the top videos in the children's song niche have close to 100,000 dislikes.