What are some good, mellow classic rock songs with recognizable instrumentation that sounds nice on piano? I have two hours to learn some background music. It can't be too overplayed or have a message that would be deemed inappropriate by a catholic school administration, even though there won't be a singer. Not being about drugs, death, or depressing things is a plus. I was thinking something like "Lights" by Journey, but I want to learn something else.
tl;dr: Classic rock songs that sound good on piano?
ETA: This is for a highschool graduation mass - songs about failing at life are a no.