Dear Mrs. Loo,
On behalf of the staff, I wish to extend my congratulations to you and Mr. Michael on the occasion of your 20th Wedding Anniversary on 1 May.
The staff is planning to hold a party for you and Mr. Michael on Saturday evening of 30 April. They asked me to inform (they meant ‘order’) you to bring Mr. Michael along with you to the office on 30 April at 6 P.M. Is this okay with you? Please let me know.
Anyhow, congratulations once again and may you two have many more happy years together.