Just wondering what I should write in an email to wish my Chinese friends a happy Dragon Boat Festival, June 12.

Any ideas of what is formal practice?

no. its not happy at all. so dont use the word "happy"

since the original reason for this festival was a chinese scholar who, after being rejected by the emperor (the scholar wanted to warn the emperor of danger I recall), drowned himself in a river.

the scholar was loved by the people and so that the fish in the stream dont feast on the scholars corpse they threw "zongzi" into the water.

zongzi is meat hidden in rice wrapped in a banana leaf.
nowadays the fillings vary (also red bean paste or dates instead of meat.

Thank you for the reply. Interesting to learn about the origin.

In that case, would "Wish you a fulfilling Duanwu" be something ones says? And how would that translate into Mandarin, or even better, Shanghainese :)

As with all holidays in China it's still customary to use "happy", in spite of the dark tone of the holiday's origins.

端午节快乐！

Are there no variations at all?

I am also torn between two opinions. My friends say its ok to say "happy..." but my teachers says "NO".

maybe the best is to say nothing.

Bump. I have no idea but I think we need to know. The celebration is fast approaching!

层层粽叶层层情，一层一层送予你：一层送你身体健，二层送你事业顺，三层送你生活美，四层送你爱情甜，五层送你财源丰，六层送你家和美

粽子节快乐！

端午节快乐 seems to be ok. chinese search engine baidu.com has it as a suggested searchphrase.

清明节is the one example where you really can not add 快乐

and its not banana leafas, is reed leafs.