Moving the sow from the litter is best as the litter will not be stressed and will be left in the area which is familiar to them.
Move sow with litter back inside (where they were born) leave sow with litter inside for a day and then move sow from pen back in field next day. Weaners will be stress free as in familiar area, radio will be on with goodies in trough and your familiar voice will make it all a very calming experience. This method makes it easier when it is time for them to go to their new homes.
Video showing sow and piglets going into the barn ready to be weaned.