Creating new account on Lion iMac using Migration Assistant

Some friends of mine have a G4 Macbook and a new iMac, running Lion. They want to create a new user account on the iMac (in addition to the existing account the computer was set up with) and then "migrate" the user data from the old Macbook into the new account, without affecting the existing account on the iMac. Will Migration Assistant do that?

In other words, they want to switch from having two computers to having two accounts on one computer (retiring the old Macbook). I want to know if Migration Assistant can be used to set up a new account on an existing computer, rather than setting up a new computer as a whole. It looks like Migration Assistant expects to write to the target computer at a higher level, importing Users, Settings, Applications, etc.

The other alternative would be to put the source computer in Target Disk Mode and just selectively import the data we want from it, but it would be nice if we could just turn Migration Assistant loose on it.

(We know how initiate target disk mode and connect the computers, etc, this is really just a question about configuring Migration Assistant).