I don't restrict the number of kids they have but I have said that if it gets too large, at a certain point, some sims will have to move away or will switch to mostly unplayed. I don't follow a strict schedule but I do keep everyone roughly generationally in synch so that the older sims age out before the younger ones. If I really get bored with a sim, I'll switch them to unplayed but usually they do become interesting as I play them.
I'm basically playing a "town" comprised of the interconnected worlds. My goal is to keep it all varied but then to see quirky interactions.
In terms of the number of kids that they have, different households do different things. It's kind of fun to go from the chaos of a household with five kids bouncing off the walls to a single sim hacking into the jungle or Brent Hecking spazzing over his cat jumping on his counter.
I flip between the houses depending on what I'm in the mood for but I make sure to play each of the various houses at some point. I will pick some favorites from among all of the households eventually based on what I have time for.
