I don’t see all that happen in one pack, but spread out could work.
Spiral staircases and bodyhair should be basegame.
What Kids really need though is imaginary friends.
Not exactly the same as those in Sims 3, but a combination of that and ROM’s familiars . Not another glorified drone either. That would be ridiculous.
There should be many imaginary friends to choose from or “adopt”. It can be interacted with and it may do chores for the kid depending on their level of friendship. They’re also invisible to everyone except to the child, but it would be interesting if kids can share their imaginary friends with Sims (of any age) with whom they have a great relationship.
“Owning” an imaginary friend reduces the chance of having a monster under the bed to near 0% or...in some case the monster under the bed can become the kid’s imaginary friend. Monsters Inc. kinda style.
Right now, kids have almost nothing and if they ever get something as tedious as an active school (why schools of all things kids can do?!) they better get many adventures to go with that.