Regarding your kids and taking off their shoes.
1. Minhag aveilim is a funny term for not wearing shoes. Is it minhag aveilim to wear slippers? To serve eggs to your family? Perhaps she was coming from the ayin hara angle and she isn’t as “nuts” as originnaly thought.
2. I’m not into ayin hara stuff, but what if your kids wore a “roite bendele” to counteract said ayin hara. Maybe they neuteralize each other.
3. Perhaps it’s the shoes that are all over the floor that really bothers her and if they were lined up neatly somewhere she wouldn’t think about it.
4.Perhaps your kids take off their shoes for comfort. How about a compromise when bubby is around, wear slippers or crocs.
5. If the kids are small, just double knot their shoes, they won’t be able to take them off. The older ones, just be open and tell them, listen it really annoys bubby when you take off your shoes, do me a favor and keep them on when she is around.