Threesome with my husband and bff

Okay, so this might be a long story. So get comfortable, go grab a snack, cuddle up, do something cause I need opinions and advice lol

Okay, so I've been with my husband for almost 6 years now. And we've had fantasies before like just kinky stuff. And well in the beginning of our relationship we both wanted to do a threesome. We were totally down for it, but then he cheated on me hella times (we were still in highschool) I know, weird. Lol okay so after a while I got super insecure and like just not feeling like doing a threesome was on my list anymore because I just felt like I wasn't enough or like what if he thought the other girls would be better than me or prettier than me. Yeah, I was really fucked up in the head lol I'm a little better now cause I mean I gained my confidence back and he's changed, he's a man now. But like idk, I still have a little of those thoughts still lol and okay so one day he was out with his boys and he didn't come home til like 5 I think and we stayed up talking til like 10 or 11am and just talking about fantasies and it basically felt like we were starting to get to know each other all over again, it was nice. And okay so a lot of it was about sex and what we both wanted and he brought up the threesome again and I'm like you know what, fuck it I'm down. But I told him, I'm still a little bit insecure about it. And he's like well we can both pick mutually. And he asked is there anyone you have in mind?? I brought up my best friend cause I mean I do feel super comfortable with her but I'm just so friggin scared to ruin shit between about all of us and I always think about what could happen and if something were to happen, it'd be on me because I basically allowed it to get to this point. And so I told my best friend about it too and she's down for it. But ugh... I'm just so scared, cause those two are basically all I have and I don't wanna put us in this situation where it could harm us. And my husband reassures me that nothing would ever happen between them unless I was there... and that he's good at emotionally detaching himself, he said it's just sex, and that this threesome is just a thing for us to do as as couple. To spice things up. And If don't wanna do it then we won't. But it's like shit... I wanna make him happy and fulfill his fantasy, and also mine cause I wave wanted to do one too but ugh it's hard. What do you think I should do?? Should is do it or no?? Lol and have you guys ever done a threesome?? If so, how'd it go?