London to Genoa

Hello, I'm planning a motorbike trip early April from London to Genoa, where I'll take a ferry to Palermo in Sicily.

I'm thinking of breaking up the ride from Calais to Genoa into two days, with an overnight stop in Besançon, and then continue to Genoa the next day via Lausanne and the St Bernard tunnel.

Does anyone have any experience and tips on this route? I was wondering if the route via Lausanne/St Bernard makes sense, or if the route via Geneva or Chamonix makes more sense? I guess my main reason for going over Lausanne is that the Mont Blanc tunnel is often very congested and the toll pretty expensive; and the route over Chamonix is quite a bit longer.

I was also wondering about the weather/temperatures in the mountains between Lausanne and Aosta early April; how big are chances that it will be icy/snowy?

Any tips welcome :)