I'd try to emphasize the Irish aspect, and the "heartwarming story of mid-life love".

It might not hurt to mention it's written by the same man who wrote "Doubt", but you'd need to make it clear that this a totally different "type" of play.

Google up some reviews and quote them.

Charles Isherwood, in his review for The New York Times, wrote: "As is also regularly the case in plays set there, the reaper will pay a house call before the curtain has fallen.... But you needn’t be a cockeyed optimist to deduce that the skies will ultimately clear for the play’s moody, broody central characters, two middle-aged farmers winningly played by Brian F. O’Byrne and Debra Messing.... 'Outside Mullingar,' ... represents Mr. Shanley’s finest work since 'Doubt,'"... Mr. Shanley’s lyrical writing, and the flawless production, directed by Doug Hughes,... give such consistent pleasure that even though we know the equations that define romcoms will add up to the familiar sums, we are happy to watch as they do."

The reviewer for USA Today wrote: "Had Shanley made Anthony and Rosemary, say, career-obsessed urbanites still living with their folks in the same apartment building, the story would seem ridiculously contrived. But by placing them in a rural setting where dating options are considerably more limited — not just by a less-dense population, but by cultural and religious mores... he makes their plight more credible and, despite some hokum, intriguing... if Shanley is raising less-complicated questions this time, there are flecks of wisdom in his sweetly diverting study."

Break a leg...