Is there point in using Sessions in this particular case?

Is there point in using Sessions in this particular case?

The client opens a website through a non-web app and thus gives an ID and
a unique security code through query strings. So the url looks smth like
this: .../Default.aspx?uI=21&sc=b2r#67!kl
For different clients, the website has different content. The users are
not more than 10 (considering that 1 client is 1 company that has many
employees(users) and for all users of 1 company the security code is the
same). So 10 users from the same company will have different IDs (uI) but
the same security code (sc) and so on for the different companies.
So is there point in using Sessions or it is sufficient to use just the
query string values for distinguishing the users? Why/why not?
Suggestion of any other, better way of implementation is welcome.