Need a big assist with this itinerary. First go round, so open to suggestions. We are experienced travelers but due to age, my days of driving in Europe are over. We don't feel the need to do and/or see everything when we travel. Lots of walking, great food, and great scenery is the way we like to roll. Having said that, we are flying in and out of Geneva and would like to see some of Switzerland and some of northern Italy. We will be traveling mid September. This is what I have so far:
Fly into Geneva
Take train to Lake Maggiore and stay in the area for 5 days
Take train from Lake Maggiore to Lucerne
Train from Lucerne to Zermatt
Zermatt to Gruyeres
Gruyeres to Vevey
Vevey to Geneva
Depart Geneva

It might be easier to visit Zermatt first, as you will pass through this area by going from Geneva to Lake Maggiore anyway.
That gives:
Train Geneva airport - Visp (train change) - Zermatt. 4 hrs journey, trains every 30 min
Zermatt - Brig (train change) - Domodossola (train change) - Locarno/Lake Maggiore. 4 1/4 hrs journey, trains about every 2 hrs
Locarno - Bellinzona (train change) - Lucerne: 2 hrs journey, trains every hr
Lucerne - Romont (train change) - Bulle (train change) - Gruyeres. 2 1/2 hrs journey, trains every hr
Gruyeres - Bossonens (change train to bus) - Vevey 1 3/4 hrs journey, connections every hr

Italian destinations on Lake Maggiore are of easy reach from Locarno, by either bus, train or ferry.
If you prefer to stay at Stresa instead of Locarno, the best way from there to reach Lucerne goes via Milan (4 1/2 - 5 hrs journey)

There are tons of more scenic alternatives like
Brig - Domodossola by Postbus over Simplon Pass
Train Locarno - Airolo - Postbus - Nufenen Pass - Grimsel Pass - Meiringen - Brunig railway - Lucerne
Train Locarrno - Fluelen - Lake Lucerne boat - Lucerne
train Lucerne - Meiringen - Interlaken - Gstaad - Montbovon - Gruyeres
etc. etc.

It's all up to you

How many days/nights?

If you have two weeks or less, can you change your flights to eliminate the backtrack to Geneva.... Fly into Geneva and out of Zurich, or vice versa? If not, I'd consider heading to Luzern first and then working your way back to Geneva. There are no-change trains for this route that take 3:15 hours. If you can fly out of Zurich, I'd approach your itinerary in reverse of your list... Vevey and Gruyeres first and Luzern last. The train service from Luzern to the Zurich airport is frequent and the journey takes just over an hour.