I agree with @PratheepArunRaj . It's good to use the same report suite for tracking the small site as well as the main site. However, you can use a Virtual Report Suite for the small site created after segmenting traffic from the main site (using some parameter).
But you will need to separate some evars in case you would like to explicitly use it for the small site, and not share it with the main site.
Use one Report Suite and create multiple Virtual Report Suites. Make sure that you capture the Domains & Sub Domains in the Server Variable so that you can create Virtual Report Suites using segmentation.
To learn more about Virtual Report Suites, click here.
To understand how many report suites are ideal for a company and why, click here.