Wishing a happy 30th wedding anniversary
uncle and aunt


well, address them as "uncle, auntie", if they understand english (ask your gf)

in cantonese, address them as 世伯．伯有

世伯 - gf's father

伯有 - gf's mother, originally, it should be 伯母. well, cantonese speaking people have many taboos, "伯母" sounds similar to "百無" (hundred + nothing / lack --> lack everything). so, it's common to say 伯有 (有 means have --> have everything)

the pronunciation is:

世伯　
伯有

imo, your approach is too "direct". maybe, try to introduce yourself, then mentioned you "heard" from your girlfriend that, it's their wedding anniversary. so, you make this short video for congratulation.

i would suggest something like:

世伯　伯友 (or uncle, auntie)

你哋好 (~ how do you do)

我係阿 Sam (supposed "sam" is your name, ~ i'm sam)

聽 mary 講 (supposed "mary" is your gf's name, ~ i heard from mary that)

聽日係你地結婚30周年嘅紀念日 (~ tomorrow is your 30th wedding anniversaries)

喺呢度 (~ here, in the video)

祝你地結婚紀念日快樂 (~ wish you a happy wedding anniversary)

bye :)

check the above text with your girlfriend, get her approval :) 

you may use the multi-function chinese character database to find out the cantonese pronunciation.

http://humanum.arts.cuhk.edu.hk/Lexis/lexi-mf/

if you're using mac os x, copy the text to textedit.app, the text-to-speech is quite good, you may learn from it. i guess that windows has similar function, which i don't have experience.

have fun, good luck la :)