Hi Marlies,
Yes, you should be able to use Track Directors as meta-reviewers, but you should definitely try this out yourself first before settling on OCS. We have an OCS demo at
http://pkp.sfu.ca/ocs2/demo/testdrive/. You can login with the admin account: username -- admin; password -- testdrive.
A couple of general notes: you can't assign/individualize groups of reviewers against track directors, but you *can* list areas of review interest per reviewer, which track directors can then see and select against. If you assign track directors to a given track, they will be automatically assigned any submissions that are submitted to that track, but you don't necessarily need to do this -- you can leave track directors unaffiliated with tracks, and have a director assign submissions. And once a reviewer is assigned to a submission, his/her name is listed as assigned, and is unable to be reassigned until free.
Cheers,
James