I do like pregnancy (as a mechanic) content, but I can see how it would be difficult to implement that in the semi-realistic world setting of this game. Even if the game did the usual thing of pretending child rearing then happens elsewhere (i.e., giving the baby to the parents, I guess), realistic pregnancy duration would mean a lot of stuy time passing, and adjusting game play would be a lot of work (cheerleader tumbles in the third trimester?).
I see little trouble implementing that into this game, because there's already a town. When the protag gives birth they have to move off campus and live in town. This means paying rent and possibly hiring a nanny, so more reasons to work some sort of job. As for how much content to set up for the children, I assume this game takes place in a four year period, ending when you finish school. That's perfect. You only need content for children up to four years old. Easy peasy. The first year is dedicated to standard baby stuff, breast feeding, taking them on walks in a stroller, playing peek-a-boo, sing them to sleep, baby talk to them. Second year includes potty training, learning to walk, teaching to talk, reading them books, giving them baths. Year 3 can involve a daycare, the kid drawing, taking them to the park, etc. Heading into year four would be much the same, and you can talk to your kid. It's pretty easy to make simple content for small children. It's only when you want to turn them into full adult npcs that you can get romantic with that I find things become complicated, but that's just me.
Edit: Oh yeah, that kiddie pool can finally serve its true purpose! XD
Edit2: Fuck, my mind is already setting up the UI. Imagining something that combines the current npc interface with what I've seen of babies in DoL.
Chat (based on age, could be baby talk, could be teaching to talk, could be an actual conversation)
Feed (based on age, breast feeding, bottle feeding, baby food, make a meal)
Play (based on age, could include peek-a-boo, drawing, kiddie pool, etc)
Bathe (obvious, if child is dirty, if you include events that make child dirty (potty training gone wrong))
Read (probably need to buy kid books to use this)
Sing (a lullaby, best used for when child is upset or you want to lull them to sleep)
Walk (is as said, could include walks to the park)
Nanny/Daycare (because you can't always be with them)
Edit3: Actually, it's probably easiest just to do a nanny, that way you don't need to create an inworld daycare. Daycare is for overachieving devs, lol. Also, nanny=opportunity to bang the babysitter.
Edit4: Nanny should probably be in the phone, not the child interface. Maybe initially discovered online.
