I tend to age my toddlers up to young adults and tweak their genetics until they look acceptable enough to me, and age them back down, but this alters in some of my saves:
-My 100 Baby Challenge: No changing at all until they're YA and ready to age up and leave their home. The matriarch then gives them a full makeover via new clothes and a haircut to try and make them look as good as can be before venturing out into the world of adulthood. As a mum with a multitude of children to take care of at all times, she simply doesn't have time to worry about the kids hairdos, weird makeup experiments or clothing choices.
-Lovelace Legacy: No changing genetics at all, hair and clothes may be customised at any time. Since I'm more connected to the sims personally in this playthrough, I value seeing the genetics be carried through the generations etc. (Minus the current grandma who threw 150,000 simoleans away in return for some plastic surgery in an attempt to find a younger man since her late husband's passing)
-My remodelling save: I have a save where I briefly edit any sim or building that my sim visits that is dire need of help, whether through questionable fashion choices or sims that are begging for plastic surgery or just silly floorplans and interior/exterior design.