parent child travel

I want to take my son (18) to Europe (Spain, Portugal, Italy, Paris, Greece) this summer as a grad present. Mostly backpacking, some hotel. Suggestions? I'm 50 so student discounts etc don't work for me but I've been to Europe in '81 on the 2-month Contiki tour - loved it, but want to do a more personal view (and a last-hurrah bonding experience with my kid). Suggestions on places to stay?