vacation ideas for Lake Garda, Como and perhaps Switzerland

Hello, We are planning a trip to Venice for four nights in October/08, then taking a train to Lake Garda, for a couple of nights, couple of nights at Como and perhaps day trip to Switzerland. Not sure where to stay at Garda, should I book more nights at garda and use it as our main place. We will not be renting a car, just and train and bus service. Is six to seven nights in this area too much. Is it difficult to board a train for a day trip or overnight to Switzerland. Thank you so much. I am sure whatever we end up doing it will be great but the more I read, the more I wonder where I should book. Thanks again Deb