Am i over reacting to my family?

You're definitely not overreacting. I would politely ask them to ease up, as you'd like to keep the details between the two of you and both of your parents.

I don't think you're overreacting at all. It is not your responsibility to make up for another family member's absence. You are not obligated to tell anyone every detail either. What I might suggest is telling them that you want the finer details to be more of a surprise so they can take it all in and enjoy it on the big day.

My FH's family is similar. They want ALL the details of our wedding and then never shared any details of his cousins wedding when I would ask.. it's interesting how people work. I vaguely give details.. show them a picture of something I purchased, etc.. but if it's something I don't care to have them know then I say we haven't decided yet and just listen to how I need to decide soon because the wedding is quickly approaching! I recently decided to forgo my dress and buy a new one, and I have yet to tell anyone on my FH's side. I figured I would once the dress arrives (3 weeks before the wedding), but I just dont want to deal with them yet.

You're not overreacting at all! It's nice that they want to know the details and be "in the loop" but that doesn't mean you have to tell them everything. Updates are fine, but remember, the more people you tell the details to, the more opinions you have to deal with. Also, I don't think it's right that the family is sort of expecting you to be your aunt's surrogate daughter--in the sense that hers is estranged from the family, and grandma expects you to pick up the slack. That's just not right. It's not your fault your cousin cut herself off from the family. Just ignore that. Do what is best for you and FH and your wedding.

When you talk to aunt or grandma, just listen to them, and if you are pressed for an opinion on their ideas, be like "that's a great idea, I'll consider that" or "we haven't decided which way we're going on that yet" and other non-committal phrases you can use to keep the conversation moving, but not offend anyone. You can make them think they are in on all the intimate details without actually including them in all the intimate details.

You're not overreacting! I get that they are excited and want to be involved, but I wouldn't involve them too much. What you were doing before was fine. If you involve them too much you will lose control of your wedding really quickly, or feel pressure to do things you don't want to do! Good luck!