A reliable webinar is rarely the result of one person doing everything. Give the host responsibility for the message, a producer responsibility for the flow and a moderator responsibility for the questions. Before the event, rehearse from the same connection and device each presenter will use on the day. Test the event link, audio, camera framing, screen sharing, recording and every hand-off between speakers.
Send one invitation that clearly says what the audience will get, when to join and where to find help. Open the event early for the presenters and production team. During the session, let the speaker focus on the audience while someone else watches timing and questions. Afterwards, send the recording, the next step and answers to anything that could not be covered live. A straightforward operating rhythm gives a webinar more credibility than a long feature list ever will.