For the Dream and Fantasy ... a
Walmart is indeed, close by. Since the Wonder and Magic change home ports, it could be an issue with being able to utilize gift certificates ... especially when not on US soil. A gift card to Hard Rock Cafe (or their favorite hang-out at a port-of-call) sounds nice ... but you'd have to research to make sure a US purchased gift card (in US Dollars) will work abroad (possibly in Peso's ... which may be subject to a transaction fee).
Sending CASH through the mail is not an option ... though it's FABULOUS when in person. For those who communicate with CM's (Facebook, e-mail or snail mail), why not ASK them if you (the guest) could buy them a gift card ... ask the cast member what type of gift card they would like. I am sure they will be flattered ... some might decline (depending on how well you know them). If I were to ask my CM's if they wanted a gift card, I am sure they would give me a LIST of acceptable locations.
Since we will be sailing on December, we will be bringing a few extra bottles of Hungarian Tokaji ... I am sure the Hungarian servers will appreciate a taste of home. While we are on the ship, we can ask what gift cards would be appropriate. Just remember, if their ship changes itineraries ... the ports (and hence, the stores / restaurants) will change. There aren't too may options for Alaska ... not sure about Vancouver or Seattle ... but when the Wonder sails into Miami, it's a different story. FWIW, there is a Walmart in Miami (8651 N.W. 13Th Terrace, Miami, (305) 470-4510), which is about 10 minutes west of the airport (take Perimeter Road). This isn't REAL close to the port ... but might be worth consideration. If that does not work ... perhaps a GC to a local eatery would fit the bill. You might think they will like Jimmy Buffet's, but they may prefer Peco's Bill's! It's safest to ASK the CM for their preference.
Feel free to send your CM's a quick letter ... invite them to send a response via e-mail or Facebook (they have limited time online, and are required to pay for internet time).