One song is What a Wonderful World by Louis Armstrong. I first discovered this song via the Robin Williams movie Good Morning Vietnam. It's also the final song at the end of the TV version of Hitchhiker's Guide to the Galaxy. I'd have this one played first (as you can get weepy).
My son I'm sure would say the next one is an obvious show of my humour but really it's to tell people to get on with their lives and to celebrate life. The song is Don't Worry Be Happy by Bobby McFerrin, an earworm of a song that came out in the late 80s. Added bonus to the video is Robin Williams making an appearance.
Sure be sad, but what I really want at my funeral is for people to celebrate the act of living and the times they had with me.