Family advice

MrsMommyofDom

So i need advice. My mom was great til i was 4. Then she married a drunk, drug addict who abused my sister and i. My sister is 2 years older...now im 27. When i was 6 or 7 my maternal grandfather adopted both of us and raised us. My mom has 15 years clean but is never around. When i was pregnant with DS1 in 2009 she gave so many false promises and it hurt so much. Now im expecting DS2 and my mom is never around i last saw her on Thanksgiving at my sisters house which im ok with. My point is, she never cares to see her only grandchild and only asks about me not my hubby or son when she hears my sister is over at my house. She tries to act like we are best friends and nothing is wrong when we do see eachother. Ive told her how i felt in the past and she will come around for a week or two...only to use us and then disappear for months on end. I dread holidays because my sister always brings her around. My sister doesnt see what im talking about. So! My plan is when i go into labor...to just tell my hubby...and only him. Im not trying to keep my sons away from their family...im just trying to protect them from false promises. Btw, my son saw a picture of him and my mom when he was a week old and said "mommy, whos that?" Referring to my mom. I told him. So there are upcoming events where i know she will be, how do i handle them? Id be completely ok with not talking to her at all. Sour feelings come up whenever she is around. I dont want to be rude, but we better off without.