В нем наши товарищи приглашают иностранных господ приехать к нам поучаствовать в конференции у нас в России с "с подготовкой доклада на тему того и сего."

Вот с этой подготовкой доклада у меня проблемы с тем как это вежливо сформулировать для иностранных коллег.

I have the pleasure to invite you and your colleagues to attend the sessions of the conference. It would be much appreciated if during the conference session you could present/deliver a speech on this and that.

Буду всем очень благодарен за идеи

Обычно would требует would или форму прошедшего времени.

'would' in correspondence requests
Would be grateful is often useful when making written requests and it can also be used in conversation:

I would be grateful if you could / would send me further information and an application form in relation to the job advertised on page 6 of your publication – reference DS 112.
http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv131.shtml