Take care of them but live and let live! They are on holiday too. Let them have fun with the other children of the group. Don't interfere in their squabbles or everybody may gang up on you.
But decide with the other parents the children's lunch and dinner times, preferably before the adults’ meal times so it'll be quieter for you… and for them!
For safety reasons, always designate an adult to keep an eye on the younger children.
Above all: never give your opinion about the way your friends bring up their children. It's a very touchy subject.