I don't know if my comments will be helpful or not, but I'll toss them in the mix.
You can't see me, but I'm giving you a standing ovation.
Years ago I happened to find a very old Readers' Digest article titled, "I Am the Mother-in-law in the Home." It could have been from the 1930s or '40s. It was an eye-opener to me. I had never, ever considered family life from the point of view of an old lady who moved in with her grown children.
She wrote about the tension that happened in the home as soon as she moved in. She had to realize that she was not a household head any more, but rather something in between a guest and a roomer, and had to adjust her own thinking accordingly. She did as much as she could to make a life of her own without inconveniencing her children, especially her daughter-in-law. I was impressed.
Now I am a MIL myself, but I don't have to live with my children. If I ever have to, I hope I can do half as well as the anonymous writer. I would try to figure out how I could pursue some interests and see some friends without disrupting the rest of my family's life or costing them very much money. If the move to my children's home entailed leaving my own friends, it would be harder, and I'd hope that I could somehow make new friends my own age.
I would hope I could be cheerful, not complaining. That could be a hard one. I hope I would learn to be a good listener.
On the other side of the coin, what I hope I would get from my children and grandchildren would be the physical help I needed (since otherwise I'd be living independently), a chance to feel useful, and a renewed sense of personal value. As people grow older and/or develop physical problems, they wonder if perhaps they're now worthless; our society exalts youth and independence. Depression is rampant among the elderly.
I hope I wouldn't be bossy, but I wouldn't mind if someone asked my opinions once in a while!
It will take some time for all of you to adjust, and it won't always be easy, but do the best you can. Talk to a multi-generational counselor if you need to. You're doing the right thing.
My best friend from college grew up in a multi-generational home. When her grandparents could not live independently, they moved into my friend's home as a matter of course; later, her other grandparents lived there. My friend and her husband always lived in houses that had an extra first-floor bedroom and bath, because they always wanted to be prepared to take care of a parent - and they were rather sad that they never did get the opportunity to do it.