I am so sorry you are going through this. It really does suck lemons most days.
Buy some cute hats that you like. If you don't like them, you won't wear them trust me. They have all kinds now. Get a good sunscreen. My dr recommended the Neutrogena with helioplex. It works good for me. Get a coverup. Something light but gives good coverage. Umbrella probably won't hurt but then go have fun at the park. Most of them here, not sure about CA :lol: have trees so you won't have to be in the direct sun.
My point is, if you are feeling up to it, there are ways to get around the sun and still have a life. You don't have to avoid your favorite things, just a different way to do them. We just got back from South FL where the great grandparents have a pool. I waited til the sun went down to swim. BUT in the mornings when my son just couldn't stand it anymore I put on a long sleeve shirt and a big hat, sunscreen and jumped in. And it felt soooo good on my joints actually to be weightless. I wish we had indoor pools here.
I know nothing about disability cause I am too stubborn to even look into it but I am sure there are others that can give you advice on that.
I know lupus really stinks, but it is possible to have a fun-filled life in between (or despite) the bad days. Just remember to rest when you need to.