A few notes on the other suggestions:
The Cours Saleya market is open every day, but on Mondays turns into an antique/flea market.
There is an elevator to the top of Castle Hill/Le Chateau, next to the hotel Suisse.
MAMAC (modern art museum) is still closed for renovations. You can consider the Matisse Museum instead, use the same ticket to hit the roman ruins next door (warning, mostly just foundations).
Along the Cours Saleya, choose restaurants carefully as the tourist traps abound (indicated by their long multi-page menus in five languages). Le Safari is a long time favorite. In general, it is better to book ahead, especially with 7 people.
With just two days, your day trip options should be chosen carefully. A trip to Villefranche-sur-Mer and Cap Ferrat (Villa Ephrussi) can be handled easily or a trip up to Eze. Monaco is a checklist item for some (when combined with Monaco). I would not go to Antibes over the others unless there is a huge Picasso fan (the beach is the big draw). You can consider taxi/ubers to help make up time and make things easier on the grandparents (private vans and guide are also available). Places like Eze and Cap Ferrat do require some walking (as does Monaco/Monte Carlo, frankly).
Pending weather, I recommend having lunch at a beach restaurant. Le Galet has been dependable, and the Bains de Castel has the best view (other than le Plongeoir, at the Port)