Okay, first of all, thanks everyone for the tips! I definitely tried all of these the second time through and did a lot better (potty maxed, all others to level 4), but still not quite there. I tried the multitasking, I made use of my fruit plants, I ditched the high chair and mostly had the kid help himself to food after dragging it from the fridge to the floor near him (he almost always woke up with hunger in bright red, I wanted to get food into him as fast as I could), usually followed by instructing a grown up to either read to him or talk to him while he ate. And he pretty well had a grown up helping him with skills all the time (I gave him the clingy trait) but I still feel like he spent more time sleeping than actually getting things done.
Is there any challenge-legal way to max their motives like you can with other sims? You can't rally the troops or write books of life for them - can they use moodlet solvers? Or do I just need to manage nap time better?
I have also found that it helps to teach them whichever skill gets a boost from their current mood. So if the toddler is happy teach him/her thinking or communication, if playful work on imagination, if energized teach movement. Potty train whenever they need to go.
I definitely tried to do a lot of this, but how do you trigger playful/energized moods? The only way I found was bathtime, but that seemed to be random (bubble bath definitely gives playful, but normal bath can give either playful, energized, or happy?). They are also apparently unaffected by emotional decor and by emotional food (silly gummy pancakes didn't give a playful moodlet).
If their communication skill is sufficient enough, they can tell a Knock Knock Joke which can give them and the other Sim they told it to a +1 playful moodlet, same if you instruct them to make a mess with their food. If they play with a toy from the toybox for long enough, they also get a +1 playful moodlet.
Energized, they may randomly get a +1 energized moodlet if they have the Wild trait and if you get the energized moodlet from the bath, you can then use a "Take Clothes Off" interaction which provides another +1 energized moodlet.
For Happy, fully finishing a meal and getting a full night's sleep provide a moodlet each. If the toddler has the Fussy trait, tell them to interact in some way with a parent to get the +1 "Got my Way" happy moodlet; the same trait can allow them to throw a fit anytime and if an adult responds, they get a +1 "Under my Thumb" happy moodlet. If your toddler is lucky with the nesting blocks, they can also get a +1 happy moodlet from playing with that toy (unlucky results in an angry moodlet instead). Toddlers with the Independent trait get a +1 "On my Own" happy moodlet as well.
Did you also know that toddlers can watch TV to raise their Imagination skill?
Toddlers, like older Sims, are also vunerable to the emotional influence of a vampire's Influence Emotions power, so they can tip the balance in your favor.