Usually when I non-rev Int'l or on a different carrier, I bring something for the crew. I don't do it with any expectations, but having been on the receiving end of gifts for the crew, and know how nice it is. A box of chocolate, and a "thanks, we are really grateful for the ride" is always appreciated. Oftentimes the crew, in return, goes out of their way to make you comfortable... though they might not be able to move you up to first class, they might offer you a few glasses of bubbly from the front, or a spare amenity kit. Do at least let them know discreetly you are celebrating something special, as most cabin crew enjoy trying to make it a special experience if they can. Congrats, and good luck