When the child is old enough to buy his own ticket, he's old enough to go it alone. As long as I buy the tickets, it's a family event.
Seriously though, I don't see this as an independence issue; rather, I consider vacations family time. I don't want to spend the day apart. They'll be out of my house all too soon (though neither of mine is in the double digits yet), and I want the time together now. I'd consider allowing a teen to have a few hours apart in the same park, but I don't want my kids heading out at breakfast with no plans to meet until dinner.
For the same reason, I would not bring along a child's friend. If I'm looking for family time, it seems counterproductive to bring along a non-family member.
Seriously though, I don't see this as an independence issue; rather, I consider vacations family time. I don't want to spend the day apart. They'll be out of my house all too soon (though neither of mine is in the double digits yet), and I want the time together now. I'd consider allowing a teen to have a few hours apart in the same park, but I don't want my kids heading out at breakfast with no plans to meet until dinner.
For the same reason, I would not bring along a child's friend. If I'm looking for family time, it seems counterproductive to bring along a non-family member.