Law problem with custody?

hi i live in denver, co with my dad, stepmom, and my sister. my dad is rude to us and he is always cheating on my stepmom. we r absolutely sick of him. my sister and i want to go live with my mom in North Carolina. we want to just get the plane tickets and leave when he is not home because he would never let us leave. we r worried that my mom will be charged with kidnapping or we will be charged with running away. im 16 and my sis is 13. what do we do?