If you place one of the big plushies on your household's lot, can your toddler interact with the plushie?
My toddlers initially get the "Babble" and "What's This" interactions, but later gets "Hit," "Hug," and "Talk" as their Communication skill increases.
Since toddlers were added to Base Game, it would be strange if those socials were only available with the Parenthood pack.
In Buy Mode, I clicked on Objects By Room/Kids' Room/Toys (the big bear icon).
When I set the Pack option to Base Game, I see 3 different plushies: Blarfy, Dino, and Uni.
Try having your toddlers interact with one of those.
P.S. Do you have the Parenthood pack? The slide is really great for learning Movement.