DH & I celebrated our 15th this summer at WDW.
I did mention it when I booked our rooms -- they asked "what are you celebrating?" so I told them!
Well, at the BC, when we checked in, there was the sweetest sign printed out and taped to the mirror over the table -- Cinderella and the Prince and it said Happy Anniversary on it! There were also 2 balloons and a couple of candy bars.
At AKL, nothing special was done, but we didn't expect anything, so we were still just thrilled to be there.
At the GF, Mousekeeping left us a beautiful 3-tiered "wedding cake" made of towels. We left it there but really enjoyed having it in our room. They also put some roses and a tiny bottle of champagne in our room!
I made all of the reservations at the same time, so I guess the CM at CRO just put it down for all 3!!!
There was also a complimentary dessert at Boma, which was funny because it found it's way to us after we had eaten WAY too much at the buffet. Luckily it was tiny!
All of this was way more than I ever expected (just thought they'd give us the Bday buttons), but it did make our trip extra special. The nicest part, though, was how all the CMs saw our buttons and said congrats to us.
I understand that you're just wondering what can happen, so I'm sharing this with you. But sometimes things don't go so well, so don't let it get you down. If they forget to give you your buttons, just ask for them! (They forgot to give my DD her bday button when we went on her bday!)