Should I tell my 6 year old stepson I'm pregnant

Ok I'm 7 weeks pregnant with my third child and my husband and his mother do not want me to tell my step son I'm pregnant they think I'm going to have a miscarriage which has never happened I carry very well but there is always that chance they want me to wait till my second trimester like the last time I feel that I shouldn't I feel like I am lying to him what should I do