Fiancé vs Mom

My fiancé proposed in December. He asked my dads permission and the whole nine yards. My dad cried whereas my mom told me that night that I “shouldn’t start planning too much because we’re not paying for a thing”. Okay, I get it, we’re 32 and you don’t need to pay for a wedding but there was a better time and nicer way to say that. My sons have asked my fiancé to adopt them so he’s their “real dad” (their wording). I guess my fiancé mentioned that or they did, to my mom. She’s been awful since then. Wants no part in the wedding and then a few weeks ago said she won’t attend and is going to try to get my (step) dad not to walk me down the isle. She’s being so mean and hurtful. All because my fiancé is adopting my sons. She (and really my dad too on occassions) are the type of people that think only they are right. She is a hypochondriac and is constantly telling me my oldest son should see a doctor for this and that and treats my youngest like a second rate citizen half of the time. Even if he didn’t adopt the boys she would not be who I would choose to keep my boys if something were to happen to me. This is the huge fight btw. If I die in the next 5 years before my oldest son is 18 my parents won’t get him my fiancé will if he adopts them. Well, it all came to a head this evening and I had a big blowout with my parents about the adoption and told them that we won’t always see eye to eye but I’m going to do what I believe is best for my children and my family. My fiancé and I have been together 7 years. He is the only father my youngest son has ever known and my oldest was 5 when we started dating. To make matters even messier, my (step) dad recently retired. He owned a construction business his entire life and always said he wanted to build my house before he stopped working. So, we broke ground on the house this year. The plan was for my fiancé and I to take out a loan to pay for the home after it was built. Construction is at a hault and they’re threatening to “take the house”. Obviously, we would just buy a different home but this would damage my relationship with my parents. Well, my fiancé is done. He said he can’t do this anymore and he thinks we need to distance ourselves and the boys from my parents until they stop. My mom is telling my oldest (who for some reason she is much closer to) that we are lying to them and are going to change their last names. She is putting him in a horrible position and making him feel like he needs to “choose”. They have my (step) dads name because he raised me and when I named them I didn’t want to pass on my fathers name who I hardly knew. We aren’t going to change their name, because it’s important to my boys to keep that. My oldest and sometimes my youngest stay at my parents house on the weekends and go do homework over there if I’m working. They’re a huge part of our lives. I feel like I’m being put in the worst place. I don’t want to tell my sons they can no longer see their grandparents because I know it will hurt them but my fiancé says that’s what we need to do. Has anyone else been in this sort of insane situation before?! I feel like no matter what I do someone is hurt or angry and I just want to lock my parents and fiancé in a room together until they all work this out!