Hi Daniel,
A quick look at your layout. It looks pretty good. So I think we can rule out ground loop and layout as primary causes. That leaves us with a very fast turn on of the FET.
Let's try two things.
1) The ringing frequency is around 120Mhz. Can you place an 1000pF 0805 COG ceramics capacitor on the input as close as possible to the FETs. Place it to the left of C65. This cap will have a resonant frequency around 130Mhz and it might with the ringing.
2) There is a higher QG version of the FET the CSD17304. This should have a slightly slower turn on speed and might reduce the ringing.
Also you could try reducing the snubber capacitance to save on the power consumption. This will be a balance between the power dissipation you can accept and the ringing. As I said before, some ringing is acceptable as long as the part is regulating correctly.
Regards,
Marc