Weather permitting, the ceremony and reception will be outdoors in a beautiful courtyard. Chances are, it will be a bit warm during the ceremony and then perfectly cool for the reception. Layers will be your best friend.
Our suggestion would be the hotel block at Marriott Irvine Spectrum. There is a 3-day music festival in neighboring Dana Point that weekend, so VRBO/Airbnb close to the venue will likely be much more expensive and the area will be congested. Last day to reserve with the negotiated block rate is August 24, 2021!
It's about 14 miles/ 20 minutes without traffic from the Marriott Irvine Spectrum to Franciscan Gardens. Best bet would be to plan to be at the venue by 4:40 to find parking, so leave the hotel around 4:15 and you'll be good to go!
There is plenty of public parking surrounding the venue, but pay attention to time limits/cost. Best bet- park in the parking garage directly next to the venue.