To be fair I haven't even made it to 20 kids... and I've been playing Sims for over a decade so I have experience on my side.
My biggest tip is to pause the game often. Pause to check on Sims, and regularly glance down at their little icons. If anyone is in the red, pause and figure out how you'll take care of them. The most red gets taken care of first. If a lot of Sims are yellow, pause and figure out what to do. The most needs red or the closest to red take care of first.
My daughter doesn't have the patience for that much pause-and-strategy, so if it takes the fun out of the game, figure out what works for you.