You'll only get hit for the Congestion Charge once but I seem to remember you mentioning
(a) that your car will fall foul of the ULEZ charge ; and
(b) that you might not be leaving Covent Garden until after midnight.
If both of those are true, you'll have to pay two ULEZ charges:
https://tfl.gov.uk/modes/driving/ultra-low-emission-zone/ulez-where-and-when#on-this-page-1