Kindly recommend the most economic way to purchase train ticket for 4 adults arriving CDG on Friday and leaving to Barcelona on Monday. Back to Paris on Sunday and leaving to CDG on Tue.
Greatly appreciate your help.
If you plan on only using the Paris Metro while being inside central Paris during your stay, then buy a single-use Paris RER train ticket for the CDG to Paris train, plus Paris Visite ticket for 3-day 1-3 zone for use Friday/Saturday/Sunday (Paris Visite valid period starts upon first usage, not when you buy the ticket), then a single-use Paris Metro ticket to get to Gare de Lyon (where the Barcelona trains departs).
For your 2nd stay in Paris from Sunday - Tuesday, likely a Paris Visite 1-3 zone, 2-day ticket, then a single use Paris RER train ticket from wherever you are in Paris all the way to CDG airport, which also includes any Metro rides needed to get you to Gare du Nord for the RER B Paris airport train.