Please don't think me a ba hum bug but I (strictly for me) do not care to have "items" as gifts.
My ExMIL gave us items for special occasions but when the marriage ended, there was a "what to do with these" because they had been given to "both" of us. We stuck most of them in boxes for when the kids were grown but then they didn't want anything to do with the "items" as they had no meaning to them. I ended up giving them to Goodwill.
The "things" that still carry happy memories are the "things" we DID together. Nothing beats a memory to me. I loved going to the musicals and Christmas concerts and treasure those memories.
Hopefully your son and daughter in law will stay together forever and ever. I'd give them special memories together if you are nearby by giving concert tickets or something similar.
In the end, stuff is stuff and memories are forever.