Take the train. Eurozone rail systems are very good, efficient and well-priced (with notable exception of British Isles!). You can do Heidelbrg-Lucerne with some transfers at Karlsruhe and Basel; Lucerne to Salzburg is pretty much a straight shot, with one change at Zurich. Failing that, look for low-cost air carriers. Here's a link to family-travel ideas in Lucerne (http://vacation.away.com/switzerland/travel-v2-cid320751-lucerne-cid350262-family-vacations.html), You might also want to check out Innsbruck (http://vacation.away.com/austria/travel-v2-cid304272-innsbruck-cid350262-family-vacations.html), the Bernese Highlands (http://vacation.away.com/switzerland/travel-v2-cid400131-bernese-highlands-cid350262-family-vacations.html ), and the Swiss Alps (http://vacation.away.com/switzerland/travel-v2-cid400039-swiss-alps-cid350262-family-vacations.html).