Mama and Papa sleep, Gretta can help herself! Gretta found food in kitchen. Couch is good place to eat.
Given the amount of micromanagement in Sims 4, I quickly gave up on any attempt to play with whole families. Even a single sim did not last long. But now with magic, I'm giving it another try. Probably won't last long, but who knows. To be honest, I wish I had given the young couple some time to improve their skills before having children, but then I would never know for sure whether being a Spellcaster is inherited using the Create-a-Sims genetics or only through actual in-game Try for baby. Well, there probably won't be any Try for baby as long as Gretta is toddling around.
Sims 4 was released without toddlers (and swimming pools, for some reason) and this caused a collossal wave of negative publicity, as fans assumed that these basic parts of the game would be sold as expansions later. It took quite a while before toddlers appeared, and when they did, there was indeed enough content to fill a mini-expansion (the $20 type). But it was free! Of course, we don't know if it was always meant to be free, or not meant to be included ever, or if they really thought they could sell it but were scared away by the howling of a thousand wolves. Anyway, a huge black mark on the game was removed. And the toddlers in Sims 4 are, like most things in Sims 4, more detailed than ever. They are also more flexible to play and have great freewill AI.
For instance, from early toddlerhood, the tykes can reach food on kitchen counters without spilling it all over themselves like they do in Real Life. They can also find the toddler bed and put themselves to sleep, although you can still put them to bed and read them to sleep if you want to. There is also a toddler tablet (computer tablet, not medication) that lets them entertain themselves while learning skills. Potty training still needs adult interaction in the beginning, but after they level up, they can complete the rest of the training themselves, it just takes longer and they prefer the diaper if left to their own devices up until level 3.
While you don't need to spend a lot of time on the toddlers, there are a lot of things to do with them to help them grow into their five skills. Taking care of a toddler is its own reward, in the sense that you may randomly get a positive "So cute!" moodlet, and also a a fairly long-lasting positive when the toddler improves a skill. Parents will also autonomously watch and check toddlers. Unfortunately, only the toddler gets better at communiaction. Parenting skills don't seem to improve with experience at all.
This would have been cuter if Mama wasn't reading from the Tome of Masterful Insults (That said, it still helped level up Gretta's communications skills...)