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.
Get one of the children as best friend.
Choose the Song of the World.
Choose the Song of the Forest.
Choose the Children's Song.
Collect the "Mysterious paintings" sticker.
Choose the Mom's Song.
Collect the "Windmill" sticker.
Collect the "Doll" sticker.
Get the cat as best friend.
Collect the "Glass shards" sticker.
Collect the "Flower of hope" sticker.
Collect the "Old kettle" sticker.
Collect the "Huge Snail" 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 "Depths of the well" sticker.
Collect the "Puppy" sticker.
Collect the "Mysterious footprints" sticker.
Collect the "Spyglass" sticker.
Collect the "Broken toy" sticker.
Collect the "Hairball" sticker.
Collect the "Lucky charm" sticker.
Collect the "Trumpet" sticker.
Collect the "Egghead Lucy" sticker.