We are traveling this summer and staying in Bellagio. We have a 3 yr old with us. We'd love to do a train day trip to Switzerland and I've seen lots of posts but not sure what's realistic with a toddler / where is a good stop in Switzerland to get off, have lunch/ walk around for a bit, and then take the train back? Most posts seem to suggest going far into Switzerland (and with good reason since it's gorgeous). I'm assuming we need to go to Varenna first but not 100% sure. Don't mind taking a touristy train up but would rather take a quicker route back if possible.
Answer in your other post about Alp Gruem.
Ferry to Varenna, short walk to the station. Transfer in Tirano (different station) & take regional trains. Figure 2-1/2 hours to St. Moritz and about an hour from Varenna to Tirano. So, travel to St. Moritz is 7 hours on the train, plus ferry rides. Plan your ferry journey with the train schedule departing as to not spend the morning wasted by waiting. Check the ferry schedule for going back as well. Don't want to be stuck in Varenna with your hotel in Bellagio.
There realistically is no quicker train. Bernina Express maybe travels faster but most routes to St. Moritz can be direct.