How long will it be before I start showing?

My best friend told me that first time mom's tend to show less than mom's carrying their second or third child. There are only two people that know about my pregnancy, the other person responsible my bipolar boyfriend and of course my bff. I want to surprise our family with pictures like the one below I don't plan on telling them till I'm at least 5 months along when my baby is viable but if I'm showing way before then I don't know how I will hide it with all the holidays approaching. This will be my third baby.