A method for cementing a tubular string into a wellbore includes: running the tubular string into the wellbore using a workstring having a deployment assembly; delivering an opener activator through the workstring to the deployment assembly, thereby launching an opener plug from the deployment assembly; pumping the opener activator and plug to a stage valve of the tubular string, thereby opening the stage valve; pumping cement slurry into the workstring; pumping a closer activator through the workstring behind the cement slurry, thereby launching a closer plug from the deployment assembly; and pumping the closer activator and plug to the open stage valve, thereby driving the cement slurry into an annulus between the tubular string and the wellbore and closing the stage valve.