Formal Japanese speeches used in such formal situations are completely different from casual speeches in daily conversations. It must be more polite and respectful than the ones you used in your e-mails for professors, and there are many rules you should keep (there are words/phrases you shouldn't use, for instance).
Here's an example for the first paragraph.
皆様、本日はこの晴れの良き日に川本家、宮下家御両家の婚礼の儀に御列席いただき誠にありがとうございます。また、新郎新婦御両家の皆様方も遠路日本からお越しいただきありがとうございます。わたくしは新婦の同僚で、本日の司会を務めさせていただきますBobbyBakerと申します。
I agree with mdchachi-san. Even if you asked to perform the speech in Japanese, it seems better to do it in English. Your Japanese speech is meaningless for those who don't understand Japanese, and inappropriate for those who understand Japanese like their families.