Shower Or Not For Second Marriage

My brother is 49 years old. His fiance is 46. They both have grown children. They will marry in May. I was hoping to get my three sisters and I could get together to take her for brunch. An adult women thing if you will. I did not think a shower was in order, just a luncheon about Janice. I have a large family with five siblings and they have grown children. The size of this event could grow quite large and I did not intend for that type of an event or to sponsor it. Is it necessary to invite her 76 year old mother or her children, one of which is away at college. My mother is 85 years old with Alzheimers but insist on coming, also on dictating the events of the day! There is nothing planned by her side of the family. Could you please give me some advice. I plan to speak with the bride and ask her feelings on this. Is that wrong?