Buy a home for my friend to live in so she can leave her abusive dh. Once they're divorced I'd sign it over to her.
Pay my own mortgage off and get my house sorted but that won't be a massive amount tbh, I'm quite low maintenance.
I'd have over 250k left, 100k to meals and medical equipment for Palestinians.
100k I'd buy a property at auction, do it up and resell, keep doing that, auction properties for cheap, have done up nicely and keep making money until I have enough to purchase a few properties outright and rent them out until my children need them. If I wasn't planning on doing this with my imaginary 500k I'd be buying some static caravans I could do some free holidays for families in poverty who don't get a break.
I'd be able to have nice holidays by saving the money that I'd not have to spend on mortgage so I'd not rush into that.