Multiple Logins and Shared Login?

We have a project assigned to a consultant group with most personnel in
India. The group is US based but outsourcing to India. The project
requires read permission to two servers and DBO permission to one server for
about 15 people. SQL authentication is only choice for me to setup the
login for them. I am thinking of creating a single SQL login and let them
share the login when they need to connect to the servers that requires read
only. For the server that they need DBO permission I will create a login
for each person so I can see what each person is doing, just in case. What
do you think about this? Please post you input. Thanks.