See
here for route.
Meet at Savi Ranch (A) at about 3:00pm. Leave about 4:00pm. Depending on traffic (sometimes the 91E is not friendly even on a Sunday afternoon), you should arrive near the Inn before 5:00pm, with plenty of time to see the lights, take a horse ride, go ice skating or eat at any one of the many restaurants in the area. (B) is or at least was public parking. Ff you want to enjoy the crazy and cruise Mission Inn Blvd, it's just one further exit up past University.
NOTE: If you want to eat at one of the restaurants inside the Inn, they have a couple going fairly upscale, you would want a reservation.
Here's a video of the last time we went a couple years ago. It was MUCH later so there wasn't so much going on. It will be busy as hell this time. The Mission part starts from around 6:32