Does anyone know of of a good place to view the parade on the Champs Elysee on Bastille Day (I know it is properly known as Fete Nationale), but I need a place to view with an 88 year old grandmother. Thoughts?

Lunch at a window table in a restaurant on the Champs (assuming they are open on the holiday)?
Just one example: Laduree.

Does it have to be on the Champs-Elysées? The view from Chez Francis at 7, place d'Alma is spectacular. Even without the fireworks, just watching the Tower light up is, in my opinion, one of the best shows in town.

I would reserve, if possible, or at least get there early.

The parade is best viewed from Rond Point des Champs-Elysées. A lot of the military equipment comes out of avenue George V, so if you are too close to the Arc de Triomphe, you will miss part of the parade (which goes in the direction of Arc >>> Concorde). Be careful not to be directly under some big trees are you will miss the spectacular military flyovers.

In terms of your grandmother's age, you can buy a tiny folding stool in a Nature & Découvertes store, of which there are many in Paris.