Bay seniors who are convinced their grandkids are the next David Hockneys might want to bundle them off to any of the many youth art classes available during the holidays. The always helpful Red Tricycle site has picked out 7 of their favorite drop-in classes. The Geezer is impressed also with Potrero Hill’s Recess where one of the coolest classes for kids 2 and up is making snowglobes using favorite trinkets. This Sunday. $28.