Wanting to make this to take to some friends who just welcomed a new baby. Any suggestions on how best to prepare/store/reheatT?

For longer term storage I would remove the chicken from the liquid and freeze separately. Defrost and gently warm the liquid part on the stove. Add the chicken toward the end until the latter is warmed through.

If you are giving it to them within a day or two after cooking, just keep it all in the refrigerator but pull the meat out before it is reheated.

I would probably leave the cilantro leaves out of any part that isn't meant to be served immediately. There's a high probability that the leaves will discolor whether it be in the refrigerator or freezer. That means I would stop half way through Step #5. Add fresh cilantro at the serving moment for best aesthetics.

Best of luck.

In the reviews, some people reported making the dish as a stew (less broth and coconut milk than in the original) and then serving it over rice or noodles.
For that, you could make it with half the broth and coconut milk, and include the extra liquid in a separate jar, if they want to restore it.
As the recipe serves about 4 to 6, maybe divide in 2 or 3 plastic boxes, so the couple can have one meal first and save the rest in fridge or freezer for another day.
Last, put the onions in a separate bag or little box so they can stay crispy or be reheated before use as garnish.