Here is the full list of all 26 Children of Silentown achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Choose the Song of the World.
Get one of the children as best friend.
Choose the Song of the Forest.
Collect the "Flower of hope" sticker.
Choose the Children's Song.
Collect the "Huge Snail" sticker.
Collect the "Depths of the well" sticker.
Collect the "Mysterious footprints" sticker.
Choose the Mom's Song.
Collect the "Mysterious paintings" sticker.
Collect the "Windmill" sticker.
Collect the "Doll" sticker.
Get the cat as best friend.
Collect the "Glass shards" sticker.
Collect the "Old kettle" sticker.
Collect the "Blue's drawing" sticker.
Collect the "Big metal ruler" sticker.
Collect the "Complicated padlock" sticker.
Collect the "Coal's fur" sticker.
Collect the "Hairball" sticker.
Collect the "Puppy" sticker.
Collect the "Broken toy" sticker.
Collect the "Spyglass" sticker.
Collect the "Egghead Lucy" sticker.
Collect the "Lucky charm" sticker.
Collect the "Trumpet" sticker.