Where stay, Vevey, Montreux, or ?? Places with half board..

Vevey is my favorite place on Lake Geneva and most hotels you stay at will offer half-board as an option. Vevey is much quieter than Montreux. There are hotels at every possible price-point. Stay somewhere close to the lake which is the older part of town and quite charming. The lakefront promenade extends on both directions along the lake and is great for a stroll. The food museum is a unique place that people don't generally go to but it's, weirdly, worth a visit.

I don't know which places might offer half-board, but did you consider Lausanne? It's a beautiful city on the lake and a great "home base" for that area.

And Lausanne is just next to Lavaux wine area with breathtaking vistas of the terraced vineyards and Lake Leman. Absolutely beautiful.

We stayed in Lausanne last fall and it was fine, but if we go back, we will stay in Vevey. Much less urban, beautiful lakefront area, good train connections (like Lausanne). The vineyard walk should be great in Sept!