Hi Bruce! 
In my opinion, it’s ideal for the username to be the person’s real name, since that’s what other members will use to mention or tag them in conversations. It makes interactions feel more personal and it’s generally easier to remember and recognize people by name rather than by their company.
Using the business name and all the professional details (company, job title, LinkedIn URL, etc.) in the profile works really well, so it’s great that you’re encouraging members to fill that out. That way, people can still quickly understand what someone does and who they work with, without the username being overly “corporate”.
Overall, your approach sounds very solid, especially for a networking-focused group 
Hope that helps, and good luck with the community!