I'm staying at an upscale hotel in the coming days and will park prior to checking in. I know a valet key should prevent an attendant from opening the glove box or trunk, but the switch to open trunk is easily accessible on the driver's door. Wouldn't that defeat the purpose of the valet protection?
On my car, when you put the (real) key in the trunk lock, if you turn it one way it unlocks the trunk, if you turn it the other way it disables the trunk release switch for exactly this reason. Test on yours and you will probably find the same thing. The valet key will not unlock the trunk or enable/disable the release. It's possible that your car uses a different mechanism such as a button marked "valet". BTW, this also prevents a smash-and-grab approach from opening the trunk, so it's relevant even if you're not handing out a valet key.
Don't forget to re-enable the release after you leave the hotel (probably by unlocking the trunk with the real key.) People find this very annoying when they didn't mean to do it.