Ooh, interesting premise. I've written for both universes, and I gotta say I'm excited to see how this plays out.
I agree that Jason's first five years might trip up LnC more than the name, but it's likely that wouldn't come up. Why would Jason have any reason to mention this to them? Unless you wanna get angsty with it (a la Mouse
) maybe have Jason be a little jealous of Clark spending time with his youngest kid? If you had Jason mention something about Trask, I can see the reaction being plausible, but otherwise not sure how boggling it would be.
UNLESS I'm picturing a much older Jason. (Figured he's grown, or at least teenaged.) Is there any chance he's still a young kid? That might change his reactions to his dad looking so different too. Although I could see a scene where he thinks our Clark is an imposter and decides to take him on.
As far as dimensional travel goes, you could always play around with a Flash-verse idea. Maybe Jason just runs so fast he tears a breach into time and jumps to their universe. Maybe our Clark has never run that fast, has to figure it out with him.
Two cents deposited.
Looking forward to reading whatever you come up with!