I think a gift card to a gourmet shop in their town might be nice.

I think a gift card is always appreciated-- but I'd say all the more if it is for an indulgence. Either a gourmet shop as Eld suggests or even to their normal store with a note to get new year's treats or similar. My mother never just sends an amazon gift card.. she sends it with a note to buy something I've been wanting but didn't need.. or to rekindle an old hobby. She always puts it much more eloquently but my point is even a ubiquitous amazon card felt special with the right note.

I'd be inclined to send a quarantine care package-- with or without a grocery/gournet gift card. Some suggestions to spark ideas appropriate to the family..

A family activity box: with puzzles and games. In my family, puzzles are mostly favored by the women but this one got all engaged (pick the team of your choice-- sis's family are all tarheel fans)

movie binge night package classicmovie munchies, a scratch off poster of top 100 movies of all-time, an apple tv gift card, etc.

Food related: kit to make hot sauce or cheese.. or go with a theme of specialty items around a type of cuisine. I always like fresh pastas, a nice chunk of locatelli, stuffed olives, etc... but so many other themes for pizza night, homemade dumplings.

Something unique to your area: many places will ship things like Philly Cheesesteaks, NYC Bagels, Chicago Deep Dish, etc.

I think something particularly nice might be provoked by a memory your son has shared from his time with them. It could be centered around food. So if they taught him to make pizza, for example, something along those lines. Or maybe not food, maybe they often played games together. I would just say, try to get specific, to evoke something about the way your son was touched by his time there.

I would follow your son's recommendation, with a note that it was "his idea because...." and send it with a small box of gourmet chocolates, flowers (or similar item).

I've sent stuff from this deli that is famous in my state. Zingerman's Deli Their stuff is good but pricey. Some of the online food places are not that great, but this one I can vouch for. But kinda costly, that's the problem. Maybe somebody knows of another good place. I like Penzey's mail order spices but that's kind of specific. I've sent "Harry and David" stuff before, it's OK too I guess. Some local markets will make up and send baskets, I've done that before, found one nearby where I needed to send food for an event . . .And if you don't like the food idea, nothing beats a big ol' Christmas poinsettia this time of year, one can never have too many in my book . . . or some other nice arrangement for Christmas. Always well received when I have sent . . .

Thank you for these ideas! If I had time, I'd do the family activity box/quarantine special. But I'm going to go with the food theme as you all suggest and support a local restaurant/shop in their city. Good idea. I also know they're observant Catholics, so I'm going to make a donation to their local Catholic Charities in their honor. I appreciate the ideas!