When it is time for the babies to age up into toddlers a birthday cake icon will appear above its head. If you press on that icon the baby will age up.
This happens to my sims a lot when they are out in public places, vampires will go to that lot and walk around for a little. I just wait till the vampire leaves in a few hours
I always get bored of my sims in the beggining because the household is small and there are no fun activities going on. As I my family grew in the sims it became more intersting but for now I would join a club or complete some whims. :)