Currently mass import is only available in Admin and only one day at a time. Suggest to make mass import of visitors available to users as they are likely to use it more than the administrators.

The mass import should allow across multiple day instead of one day at a time.

Suggested fields for importing
Scheduled Arrival Date
Scheduled Arrival Time
Scheduled Departure Date
Scheduled Departure Time
Person Visiting Name
Person Visiting Email
Visitor Name
Visitor Email
Visitor Company
Visitor Telephone Number