How do you suggest we get from Paris (or Brussels, as we may make a day trip there) to Madrid. We are a family of 4. We thought about driving, and thought about the overnight train, and thought of flying. The flying option is appealing but whenever I try to make reservations, and then proceed to payment, they double the price. Please help with your experience!!!
See http://seat61.com/Spain.htm for doing it by train. (Just skip the UK to France bit.)
A budget airline is your best flight option. Fly either Vueling or easyJet from CDG to Madrid. Or if you're willing to take a long bus ride from Paris, fly Ryanair from Beauvais to Madrid. Fly Ryanair from Charleroi (south of Brussels) to Madrid.