I suggest the following
pressure regulator -> 1/4″ male x 1/4″ male NPT -> 1/4″ female x 1/2″ male NPT (model #: HDA30300AV) -> 1/2″ female x 3/4″ male PVC (Model #: PVC 02112 1600HD) -> valve.
All connections threaded. Use thread tape, be careful. I see a chance of clogging the orifice with stray thread tape.