Note: This answer was originally intended as a clarification to a comment I created on jakebeal's answer that was well-received, but I ended up expanding it significantly during the writing process to the point that it can mostly stand on its own.
As jakebeal mentioned in his answer, it is probably best to ask for feedback from the participants (hereafter referred to as authors) themselves so they can clarify how they want to be attributed. However, you need to ensure that communication between you and a certain author does not interfere with the other authors. In essence, this means there are several ways to go about this.
The first way is to send a mass mailing to all parties, with the addresses in BCC. This means that if one of the authors inadvertently presses "reply to all" on his mail client, his email does not reach the other authors. However, using BCC in this manner might mean that they don't reply. There are certain mail clients and mail servers that mark emails sent to a BCC mailing list as spam, and your authors might not notice it. Indeed, many companies send spam marketing mails in this way, but this isn't a marketing mail, but rather a transactional mail. You are asking for the person to take an action, not just inform them about the latest addition to your website.
In addition, such a mass mailing would have to be worded in very general terms and probably would appear obviously mass mailed. Some authors might not like that, which could have a negative effect on your relationship.
Because of this, a better alternative might be to send the emails individually. this allows you to make the email look slightly more personal and avoids most spam filters because you can put the party in the To field. It does take more time, though, so be prepared for that.
As jakebeal mentioned, a good starting point to help the authors save time clarifying their honorific and lecture is through their web presence: either their website, the website of their primary institute, or on the honor list of any award they might have won.
One final note: most academics are quite busy and some of them might not want to "waste" their time on clarifications like this. If the academic or their department has a secretary or a general administration, they might be able to help you with simple actions like their honorifics.