Hi I am taking 30 champagne glasses (they are my favors), candle holders, and shells, all of which are breakable. We bubble wrapped them like Jenny said and we (some of my guests are helping) are carrying this on the plane. Anything that is super breakable I would carry on the plane. I had a glass item in my bag on my last Jamaica trip and it did not make it. If you have ever seen them throwing those bags and piling tons of bags on top of bags, you know that it is pretty scary to check glass on a plane.
I had originally planned to ship most of the stuff. I was told by my WC that if I mailed my table decorations to her, there was a chance that the items would get caught up in customs and not make it to their destination. After my last trip, I sent some clothes and shoes to a lady that I met in Jamaica (for her daughter) and she never received them. I think in order to ensure that your items arrive, you have to take them with you.
Good luck with the planning!