Of course you should at least hold the webinars in English. The more languages you can offer, the more users you will have and thus reach potential customers.
Plan time for questions from participants. You will have virtually the same contact and consulting opportunities here as at your stand. If the customer is there, give them the opportunity to ask questions. It is advantageous for this if, in addition to the host, other people are present who can answer the participants' questions parallel to the webinar.