Yup. use 3-way solenoide valve. It has a port as vent to release the pressure. But may be you have to install screen connector at this vent port to avoid the mud dauber insects build nestle in it.
Is the dP constant?. As I know the Cv is only depend on flow, dP and SG. You will need P inlet to calculate the maximum allowable dP accross the valve. From this dP allowed, you will find whether your valve is away from caviation or not.
But we need to know your process. what is the process fluid?
