I did the "California Trifecta" way back in 1988. We were there prior to, and over Memorial Day Weekend. I have a couple photographs from Yosemite with Dogwood blooms. I didn't have a field camera back then, so we took a 4x5 monorail. Didn't do much hiking, probably never ventured more than 100 yards from the road. Due to this, I don't have many negatives from either Kings Canyon or Sequoia. We spent the bulk of our time in Yosemite, the roads to the high country were open.
Others should chime in here, but I don't think Sequoia or Kings Canyon are as photographically exciting and would probably skip them on a future trip. YMMV, and I expect the hikers will chime in to tell me that I need to take some hikes to get to the best photo opportunities.
Have fun and enjoy your trip,
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