I'm not huge on child gameplay but I usually make my sim couples have at least one child. I like sims with a history and family legacy behind them.
Remember they can have children from YA to Adult life stages, so there's plenty of time. I either make them have a child right at the beginning or before they age into elders. I also play around with lifespans a lot to make sure they have some child-free time (for building relationships, advancing in career, skill building etc.) I would maybe suggest doing that if you don't want to handle lots of stuff at once. You can always age up toddlers and children if you feel it gets too much.