My parents will be staying there & leaving their car while on a cruise. They're also going to have a lot of valuables in their car. How safe is the parking?

It's okayish, but as other have said, it's a real gamble leaving valuables in the car for extended periods of time

The parking structure is safe, however regarding special valuables probably best to make an arrangement with the hotel staff on that

They may have some sort of safe box where they can put all their valuables , the parking seems ok,, but you never know

I wouldn't recommend it