re: Vacation ideas for elderly mother

How about taking her someplace that's nostalgic or meaningful to her? At this stage of her life, she might be more entertained by a visit to an old hometown, or a place where she lived as a child, or her old college campus rather than seeing an entirely new place. If the point is to spend time with her, then you might not need to travel very far at all.

Does she having living family that she rarely sees? She might like a trip to see a cousin or childhood friend she hasn't seen in years.

I'd be more concerned about making her happy than entertaining the rest of the family. You're also setting an example for your sons on you might like to be treated when you reach that stage of life.

Wheelchair tourism can be very challenging, esp when trying to accommodate a group including active teens.