I think the main problem here is that everyone is being a little rude here, other than your mom. Maybe it is because you are family that you feel that there is no need to be bounded by the typical etiquette rules...but still, I do believe that BECAUSE they are family, we should give them even more respect.
First off, it is not cool to be accepting guests in your bedroom when you have a living room, a kitchen or a deck to use. The only time I visit someone in their bedroom is when I am visiting a dorm student or a friend who is renting just a room (not the entire house), and they don't get along with their flatmates (so we ended up closed up in the bedroom).
Second thing: it is not really acceptable to be putting your guests in a room where there are not enough seats.
Third thing: We try to have clean chairs and tables, and hopefully tidy the room a little when we have visitors.
Fourth thing: If the place is small, without enough chairs, and we don't have time to clean, then we should meet outside. In a cafe or park or restaurant, depending on the budget.
Fifth thing: It is in NO way acceptable to be fiddling with your ipad, phone, computer, tv etc when you are visiting or having a visitor. NO WAY acceptable. If you cannot give your host or your guest your attention during your visit, then you should either time the length of your visits to suit your attention span, or you should change the nature of your activity to suit your ability to focus. It is especially rude to use your HOST'S electronic items as though they are your own, during your visit, and in the middle of your conversation. I just cannot believe that you would come to an etiquette site and expect that posters here would endorse that.
Now I am not trying to say that people with ADHD cannot be accommodated. I am saying that there are other ways and alternative solutions that suit any level of ADHD - solutions that will not result in a guest being rude to their hostess or otherwise.
Sixth thing: Seeing that the room is rather small and the nephew is not part of the visit, he should not be there for the duration of the visit. It disrupts the visit and changes the dynamics. It is rude for him to be physically present, but not socially available to anyone else in the room.
Final thing: I really think (and this is just my personal opinion) that you should stop visiting your aunt in her home. Just take her out for coffee, tea, or a hot chocolate every week or so.