So long as the frequency doesnt go out of the range of the core, or cause saturation (which is a risk with lowering the freq), it'll probably be ok, and its only a minor change.
The circuit would probably be better with a trimmer to fine tune the freq o/p of the driver chip anyway, then you can 'find' the peak of the trans resonance with the caps.
I suspect that the input chokes were probably not 'designed' all that much, they do not so much play a critical part in the operation of the circuit, more to prevent switching noise from going back into the supply, or radiating from the supply wires.