I'm not in your field so take my advice with a grain of salt. In my field if you are waitlisted, the chance that they will offer you generous funding is low anyways. Thus, if I wanted to secure admission, I would definitely tell them recognizing that they are unlikely to top up the award very much if at all. I wouldn't worry to much about the tuition fees issue. The department admits you and with a fellowship you look like a free or cheap researcher and TA...something departments love.
