Do they know a Disney park exists outside the US and that one of them is in Paris?
I would just hop on the train. Let's see if they figure it out when they see the Mickey head on the boards in the stations/trains. Hopefully they don't, because then the first thing they see when they exit the train station is the Welcome Sign.
One thing to keep in mind, how well can your kids handle things being different? Not just in the rides and CMs, but also, that Pirates or Space Mountain are in different locations. What is on the left in Magic Kingdom might be on the right in DLP.