Hi Dear, hope you will find this message in good health.
I have read your provided description, regarding new "customer login and activity" management Module for your already running site.
Instead of your provided details are clear, but I have some questions to ask for my clarification.
1. The secure client portal would allow multiple users for our client
here I have to ask that please can you tell me what type of clients you are serving, i.e you have said multiple users for client, it sounds that you have a "group based" client and users.
Second thing is that, Can you please tell me what do you mean by "secure field". is this a security related field (like captcha etc) or some custom field for specific client so that you would know which customer is requesting.
Looking forward for your worthy reply
Thanks
Murtaza