Initial: This reminds me of my late grandparents. Their whole body language with each other... they are comfortable friends who have been thru it all together. Congrats to them!
Technical: Their natural closeness is depicted well here, however their straight on stance in the composition and the flat lighting leaves a snap shot feel to it. Not that it makes it terrible, .. snapshots are valuable. But if you had been able to do something to kick it up a knotch - like help to arrange their positions to each other, use a more solid background, or leave more space between them and the background to give less dof or focus on the background - then I feel it may have scored higher.
Overall, I love their expressions, and in the end you were right to just catch it.