Things to do with my son

Hey folks! I'm going to visit Barcelona first time with my son, who is a huge football fan. We will go on a game against Villareal and visit Dali museum in Figueres. Is the weather good for the beach in mid-May? Is there a place on the street where kisd play football and my son might can join to play for fun? What else would you recommend to do that is not the usual things but great for kids, not necessarily football realted.