It usually depends on the family I play, I like playing with family oriented sims, so they usually end up having 3+ children. Majority of my other sims don't ever have kids or just 1 or max 2.
Currently the largest family in my game is my vampire Werner, his human wife Leslie, their adopted daughter (now teen) and then their 4 vampire kids (one is now teen and the rest are children). I totally feel you having 3 toddlers at the same time is very stressfull XD I actually had to stop playing this family for a while when the kids were toddlers as I was loosing my nerves :D The kids were crying all the time, when I called nanny to help, they did nothing and stood there. I was seriously considering taking the father and leaving the family XD But he wouldn't do that, so after a few weeks I calmed down and returned back to the family and raised the toddlers... Well, I am very happy that they are all children now, but since they are vampires I can only go to the park with them during the evening/night which kinda sucks, but somehow other human kids are there even at night :D I always wonder how can their families let them roam alone at night XD I wish there was a mod that would force some kind of curfew for npc children to appear at night and being seen out and about during school hours...
Anyway, I think raising big families is a lot of a challenge and only certain sims are up for the challenge... I would never be able to play the 100 baby challenge voluntarily XD
The best picture that I actually managed to make with all of them was right after when they decorated the tree and not even like 2sim minutes later it caught on fire :smiley:
https://i.imgur.com/Ax2FiIE.png