Then your kids could not use the remote they come with. unless there was a way to rig both somehow..? New cab 1L is kind of kid friendly it does not have an antenna like the old cab 1 And seems like it could take a drop. Would certainly not want to hand my 4 year old my cab2.
Yes they can use the remote that comes with the LionChief set. Why couldn't they?
You can run LionChief locomotives on the same track at the same time as you can with TMCC/Legacy engines since LionChief was designed to work on fixed voltages like TMCC/Legacy is. You just have to use the LionChief remote for the LionChief engine and the CAB-1 or Legacy handheld for everything else.