Los Lobos/Artpark Query

Val and I will be attending the Los Lobos (what a great frigging band) show tomorrow, Tuesday, August 29, at Artpark; the free show is outdoors, which leads me to these questions, the response which I hope will be better than the overwhelming reaction to my shoe polish question.
What happens if it rains before/during one of these free shows? Do things still go on? And while I know that Artpark has a policy against bringing food or drink into the facility, can you bring in chairs and/or blankets? Val and I last caught Los Lobos opening for the Chieftains at Artpark, which was a tremendous show, and can barely wait for show time.