I completely agree with adding another night or two to Lucerne. I would take that day away from Munich or possibly from Salzburg. I have been to all of those cities, and I liked them all quite a bit. Sometimes when I plan trips, I take days away from cities that I'll likely return to for future travel. For example, where I live, Paris tends to be the airport with the cheapest fares and most direct routes. So when I plan, I'll take days away from Paris knowing I will end up there again. Looking at your itinerary, your "Paris" is Munich. Munich is easy to get to and close to other areas that might be fun for future travel. I've been to Munich twice. The first time we stayed three nights. The second time, I did Munich on a day trip from Salzburg. Because I'd been there before I could schedule a day for my daughters that would allow us to see a lot of the things I knew would interest them. I don't think I'd get the Euro rail pass. If anything, I'd get the Swiss Rail Pass. Then when you are leaving Switzerland, go to Buchs SG., and change then to an OBB train for the remainder of the way to Salzburg. When you go to Munich, look into the Bayern ticket which ends up to be rather inexpensive. You need to use a specific machine that sells the Bayern ticket and not the OBB office. My girls and I went to Munich round trip for something like 50Euro, total!