Paris, NIce and Sicily help??

Nice is cool! Just back from there for my second visit, on a wonderful RS tour. But be aware that the beach is stony. Not a sand beach. August is most crowded time of the year there as well.
There are, I think, a few sand beaches on the Riviera but beach isn't one of them. But it is a great city with wonderful food, museums, etc. but if art and food isn!t your thing, perhaps Paris is a better choice. More variety perhaps.

Depending on how many days you really have in France could affect my recommendation. If you plan the trip with the idea, two nights equal one full day, you will find that you can run out of time quite fast. If you have seven nights that really is six days and that could be enough to spend in Paris and Nice. I would do four days in Paris and two in Nice. You can connect the two easily with trains and when you are within 90 days of the train journey you can buy your ticket for a reduced price. You can find more information on rail at www.ricksteves.com/rail. I also recommend try and fly home from which ever city you visit last that way you don't have to spend the time and money to get back to a place you already visited.

My wife and I are about your age and love to experience new cultures also , we did Paris and nice a few years ago .we flew from Paris into nice , stayed in port st Laurent right on the French Riviera , beautiful , we only stayed 3 days /2 nights , should have stayed a few days longer!!! 1/2 hour train ride to Monaco one way and 1/2 train ride the other way to Cannes . Loved it . The train ride is about 5-1/2 to 6 hours from Paris . Plane is about 1-1/2 hours

I haven't been to Nice so I can't compare it to Sicily, where the beaches are wonderful.