very confused with my trip

I need your opinion because I'm completely lost... I'm a tourist, it's the first time I'm going to the USA, I have a trip booked from March 15th to San Francisco and the plan would be to go from San Francisco to Yosemite Park on the 18th until the 21st, on the 21st I would go to the sequoias park until the 23rd and return to San Francisco on the 23rd and return to my country on the 25th. I have been following the weather conditions and I am very discouraged and not knowing what to do. I've already started canceling accommodation but I can't cancel flights and I don't feel like losing any more money.

I don't know if it's worth going and hoping for the best to try visiting the parks. Do you think it's better to reschedule for May and make my initial plan paying twice as much?

Another option would be to buy flights from San Francisco to Las Vegas and go to the Grand Canyon for 5 days and return to San Francisco.

Thank you!

edit: Hello again, I'm still very indecisive about what to do. I started exploring Big Sur, but they say that due to the rains, the roads may close. Then the option to go to Las Vegas and visit Zion Park or even the Grand Canyon may also be risky due to snow. The weather is not being my friend.

On the other hand, if I reschedule, it would be for May (when I have the possibility to take vacation). Do you think in early May Yosemite and Sequoia can already be visited?