Thanks for all the good ideas. So far I am leaning towards a transistor, as it is the most cost effective I can find, as well as having the smallest form factor. As the centerpieces only need to be functional for ~6 hours, and need to be completely iscolated hence DC power, and small enough to fit in the bottom of a glass vase.
The SSRelay was very intriguing, but the only part in the form factor I liked was $27 a piece.
I have never worked directly with a transistor before, and will be making a stop off at the local radio shack before hacking apart the Velleman Kit I have at home. It will take some playing with.
If anyone can recommend a transistor or schematic I would be very appreciative.