You don't say where your son is in Italy, but in any case you would want to fly.
Paris to Italy is a long way, and it's right through the Alps. You really don't want to drive it since you probably don't have that much time. There is train service, but we've never done that so can't really comment there.
We only drove it once, years ago, and took several days traveling between Rome and Paris, stopping at numerous places along the way. But I still recall that the total was still a good deal of driving.
Note: If you fly into Paris to go to Disney, remember that
Disneyland Paris is quite a ways outside of town. There are trains that run right from Disneyland into Paris.
March is Dream season. There are 4 hotels to choose from, all right there on Disney property.
Sequoia lodge: 28 pts S-Th, 33 pts F-Sat
Newport Bay Club: 30 S-Th, 35 pts F-Sat
Hotel New York: 33 pts S-Th, 38 pts F-Sat
Disneyland Hotel: 45 pts S-Th, 50 pts F-Sat
The Disneyland Hotel is the nicest, and right at the entrance to the park. The others are decent hotels also, but are located a few blocks away. You walk through a 'City-Walk' type area to get to the front gates. I say City-Walk because it's more like Universal's City Walk than it is like Disney's Downtown Disney.
Now that the MGM studios are open there too, things may have changed. (MGM opened this past March). Anyway, you now have two parks to go to, and the free passes are good for both parks.
We stayed at the Sequoia Lodge which was very nice. In low season it's only 26 points a night, Sun-Sat.