Toddlers: Do you max all their skills??

@Simmerville Parents can use the "teach to say sorry/please and thank you" interactions with toddlers, and I believe it will influence both the communication skill and the related character value. They also get the same hit to responsibility that children do when making messes, and I think a few other interactions can have some effect on character values, but it generally moves the values by a smaller amount than during the child stage. I've never seen a lot of benefit of trying to work character values with toddlers because the gains are so small and their regular skills take up enough time if you play on normal.
There is a permanent trait that they get if all their toddler skills are at 3 and then a different one if they're all at 5 (except potty which maxes at 3). They both give permanent boosts to the speed of skill gain for all future life stages, in addition to starting their childhood with a skill boost. There is also a random happy moodlet sims can get if they have those traits because they remember a happy childhood or something like that, but I can't say whether that continues into adulthood offhand. I know my kids and teens get it.