I believe that it was mentioned in the first webinar, that there are participants from more than 70 countries in the GoFly Prize. So for many people, English will not be their first language. I would then suggest following:
As American English is not always very easy to understand, make an effort for clear pronunciation.
Avoid terms which might not be commonly understood. E.g. during the first webinar, "tbd" was used a few times.
Avoid difficult terminology. E.g. an expression used in the first webinar was "solution agnostic".
The Master Lectures and Webinars are an impressive initiative. So lets make the most of it.