Which one of this packs is essential to your gameplay?

Truthfully none of the packs listed are essential for my gameplay but they come with nice additions. I voted for Kids Room because it's the pack that introduced Void Critters to TS4. Void Critters have appeared in items and clothing after that but here you can get the card collection (with foil cards), battle station and wall decal. With those and the puppet theatre it's just nice to have something especially for kids.