As long as your mom can handle all of this, go for it.. If not maybe do a quiet meal with her. Later do the big meal with everyone else.. Or opposite do a big meal with everyone else and take her some plates of food.
35 actually does not sound that big to me, but we have a huge family and all of them live here in town.. It is a blessing and a curse..
What we do is whoever is hosting provides the main dish and the Iced Tea and coffee, in this case maybe you could do 2 turkeys or a turkey and a ham..Also there are a ton of places.. even HEB roasting turkeys that you can pick up..
Then make a sign up list of the other side dishes. and items needed.. . Dressing, mashed potaotes, green beans, sweet potatoes,rolls, paper/plastic products desserts..
We have learned to never exclude anyone.. The more the merrier and no feelings are hurt.. . Also usually I am the person that comes up with activities.. Maybe you have a crazy person in your family that always has ideas for activities..
I always have a puzzle going. We have basket balls, horse shoes, volleyball. Jump rope and hula hoop contest.. we do a giant Simon Says and let the oldest and youngest call out.. After we have eaten we go on a huge walk around the neighbor hood.. I hand out kazoos.. (outside toy) .. And we make a huge parade..