Those switching devices are gonna get hot on that board?... If the coax works - use it, else have your gate drive send and return tracks above and below each other on the pcb... 2mm wide.
- - - Updated - - -
perhaps you should study some layouts on some existing product?
The pcb layout definitely needs a proper engineering to be efficient. I will check what I can find about similar devices.
The induction cooking device are a bit different, but i will try to find a similar design to mine.