I have to invite the principal of Model School for the Annual Inspection Day of our school. Since the post of our Principal is vacant, he is also the acting principal of our school. I wrote:
I am very pleased to invite you, on behalf of all the teaching staff of City Model School, to attend the Annual Inspection Day of our school which is scheduled to be held on the 29th of this month. Being our patron, your presence at this occassion will be highly encouraging for all of us.
Yours truely,

How does it sound? Is there any grammar or other mistak in it?
sound- The first sentence sounds wordy, and seems to have too many prepositional phrases. I think you can eliminate 'which is ... held' and just use 'on'. The second sentence seems very nice, and would give me a good feeling if I were the patron.

grammar - truly

occassion occasion