Welcome aboard the RoadTrip America Forums!
There is simply no way that you can drive to all your intended 'targets' and spend any meaningful time at them in only four days. Under the best of circumstances, just making the loop by car would take two and a half days (with no sight-seeing time whatsoever!) Add in the facts that you'll be driving through some of the most horrendous traffic in the US, and that Tioga Pass (CA-120 east out of Yosemite) will NOT be open in April, and you're looking at closer to four days just to drive. That would be fin if all you wanted to do was to sit in the car, burn gas, and watch the world go by outside, but not for a tenth anniversary trip.
If you've already booked the plane and car, then I'd stronly suggest that you stick to Las Vegas, northern Arizona and the Colorado River. That would include Las Vegas, the Grand Canyon and perhaps an overnight in Red Rock Country around Sedona. but not much else. If, on the other hand, getting to the ocean is paramount, then I would suggest skirting Los Angeles to the north and heading for Santa Barbara, a unique shore community with plenty to offer.
So, since you can't do everything on your wish list, your first order of business is to decide on what your priority is. I almost said 'priorities', but I think you have to pick just one. Once you do that we can help you make the most of your very limited time.
AZBuck