If you have your heart set on doing this, you can make an FE holder and then secretly put gifts in yourself, so your grands will be excited and surprised, but you don't have to join someone else's list. Remember, even if you got on a list, at this late date, you'd have to provide gifts for those cabins, as well. Can you get together gifts for, say 10 staterooms in two weeks? It would be easier to just keep this one in your own family.
That said, we haven't participated. We see them and are excited for the recipients, but I didn't miss it for myself and neither did my kids. They were more interested in what the ship had to offer than what other guests might have had to offer.