Gifted diecast vehicles – in need of some cleanup. Advice?

Hello I had my son with me at work, and a kind hearted customer gave him some cars that were sitting on his garage shelf. My son was thrilled and it created a really cool moment between my Customer in his 80s and my son six years old.

Up until this point, my son hasn’t really taken care of his cars. He’s played with them like they were his job.

My son really wants to clean these up and take care of them.

Can you provide any advice on how we can get these cleaned up and possibly looking shiny again? We’ve not done much with them as I wanted to seek advice first.

Thank you