I think it would be cute for little kids to have their own pretend dj booth. They could do little dances like the chicken dance, hokey pokey, and just silly dances like that. Everything would look really like colorful plastic, nothing they could hurt themselves on, but would give some sort of creativity to the kids.
Most little kids really want their parents to "look what I can do!" so maybe there could be some interaction where they say that and then do something. It doesn't have to be anything amazing but it would something they are learning to do, so they are proud of themselves.
I think kids should make funny noises too. Make animal noises or something.
Little kids just like to run around laughing sometimes. Just the joy of running around and maybe even they like someone to chase them.
Kids should be able to sing their own little songs too, it would be so cute, especially if they sang together.
Mischievous young sims could copy something someone else is doing or saying, up to a point. Sometimes mimicry is just a way to learn too, not meant to be annoying.
You know sometimes you get a big expensive toy and while you are putting it together the kid is over playing in the box and having a good time. Just a big ol' box would be a good toy. They could color on it and pretend it is anything. Pets can come in too!
Sims of all ages should sing to their pets. I would sing to my pets and they seemed to like it.
Young sims can definitely teach another baby sim how to start talking and they should play and learn together.
Sometimes kids like to play with each other's hair, so you could have an animation of them sitting on the ground together. One facing forward and the other behind them. One is playing with the other's hair. Then you go into create a sim for a second. Then some pretty unique hair styles come up, just messy with lots of braids or bows all randomly place, like kid likes it. Lots of strands of beads and hair chippies, barrettes and stuff. Then you go back to what they are doing and they will start moving their hands and make that hairstyle.
You could have two little sims facing each other and doing a sort of clapping game, rhryming game with movements, stuff that kids learn to do in school.
If you had enough of these kinds of interactions you could sort of have a preschool going on, with lots of stuff they do.
Maybe they could actually drag a blanket around for comfort? Hold a toy and carry it everywhere, actually out and visible for the world to see?
If they lose it or grow too old for it, they could get sad for a while. Or they could secretly still have it, just don't let anyone see them with it.
You could at least let them pick some flowers for their parents or and apple for the teacher and that is the very start of gardening skill.
You could have a parent sim pick the child up and let the child reach for something. This could be an animation used for a lot of stuff. Like a kite stuck in a tree, picking an apple off a tree, petting a cat in a tree to get it down, reaching something off a shelf for their parents, so they think they are helping and being a big kid for their parents. They could put a star or decoration on a tree like that.
If a kid makes a face too much it could "stick like that". For real. It would be so funny for a little while. You'd have to take a nap to get it to go away.
I see kids "Enthuse about candy" But tell me, is there actually any candy in the game? How do they even know what it is? There should be a special candy tree or a place to get some. If there is a way to actually get candy in the game, someone tell me?
When I was little I would drag out pots and pans or get into drawers and pull things out. It was fun to bang on pots and pans. I would play inside cabinets too.
I was afraid of random objects when I was a kid, sometimes things just look like they have a face, I guess. Maybe little sims could be really afraid of a certain thing, so they don't like going into a room if that is in there.