You don't have to do that before you meet with them. You can meet with them. It's not up to you to make sure that the people you meet are registered. That's my responsibility.
However, if they aren't registered, I would ask you to help me. Tell them that they're lobbying on a bill or a policy, for example, and encourage them to contact my office. If it's an organization that meets with you only once, it doesn't meet the current 32‑hour threshold. In January, though, that threshold will be reduced to eight hours, so it could meet the threshold from that point on. It would then have to reach out to us.