Yes, your Terminal steps appear correct, I personally always replace all the HighSierra 5 IOUSB***.kext for another reason, but replacing only "IOUSBHostFamily.kext" you will get all input devices working but @ASentientBot discovered that to fix iSight Camera also other 2 IOUSB*** are needed in conjunction with the first one. I don't remember exactly should be this IOUSBFamily.kext and probably another. But if iSight is working on Beta 11, you don't need them.
I just replace IOUSBHostFamily to let the built in keyboard and touchpad work (they're internally connected by USB 1, which is removed in the new kext) and IOUSBFamily because that fixes the iSight camera for whatever reason. MacBook7,1 here.