Nooboos have never evolved beyond burrito babies. However, some of us use CC baby legs, skins, hair and outfits to improve their appearance. There’s a list of baby CC here: http://nraas.net/community/Babies-Toddlers-Children
You can also use CASt on their blankets using NRaas MC.
As far as activities, there’s the stroller from Generations EP. From the TS3 Store there are the baby swings, the play mat and the changing/bathing station.
Sandy at ATS3 has some items for babies as well: https://aroundthesims3.com/objects/function_kids_furniture_03.shtml