We have been that exact week 4 out of the last 5 years. We typically are in the parks from Saturday through Wednesday. That Sunday (and Saturday) are typically great with the crowds because the So Cal annual passes are blocked. (I know you aren't going Saturday, but Saturday I think even the level above SoCal is blocked and we have always found it to be a great day). That is often the last week that the So Cal pass holders can attend on weekdays, so we have always found Monday to be packed. (Tuesday also feels pretty packed, and on Wednesday the crowd lightens up again).
As far as weather, more often than not, it is cool in the mornings, warm/hot in the afternoon, and then cool in the evenings. I have definitely wanted a jacket or sweatshirt in the evenings more than once.
As far as parking, we have always walked from where we were staying, so I don't know. Even the busy Monday and Tuesday, the first hour or so the park is open isn't bad, so if you got there before park opening I would think it would be fine.