I'd say either Come From Away or A Doll's House, Part 2. The former is quite moving at parts, but very fun and ultimately uplifting; the latter is not exactly fluffy, but it's not heavy either and has some big laugh moments. Both are roughly 90 minutes, no intermission.
I am a firm believer in serendipity- all the random pieces coming together in one wonderful moment, when suddenly you see what their purpose was all along.