Kad je bal, nek je maskenbal
When it is a ball, let it be a masked ball.
The English equivalent is:
In for a penny, in for a pound.
Ana: Neće li to biti previše?
Ivan: Ma, kad je bal, nek je maskenbal.
Ana: Won’t that be too much? Ivan: Oh, in for a penny, in for a pound.
I would say that it means something else
“If it has to be, then let’s really do it”
John, what you wrote is the correct interpretation.