I have rescued an 18month old Retriever from an animal shelter.  He seems to have had some training but whenever we wnat to play he mouths us, he has sharp teeth and although he thinks its fun my children are 9 and 7 and im afraid he will hurt them.  Any ideas to stop him.  Also he is being walked on a body halter with strings that go under his legs and they have rubbed him raw, I have treid a Halti and he hates it always lying down trying to get it ff his nose, i have also tried on a nromal lead but he pulls me off my feet, he reacts best in the body harness but im worried its really hurting him.  Any ideas??

I think you're right to be worried about the harness hurting him - one of the best harnesses I know of is the Stop Pull harness from HiCraft...He's rather old to still be 'puppy mouthing' so I'd guess he's never been properly taught that biting/mouthing humans is a 'no no'.  Ask your children to make sure that when he starts to stop playing with him for a few moments.  Make sure that they don't play with him in a way that encourages him to mouth them (no running away so he chases them, no teasing him etc.) and encourage games where he *can* use his teeth appropriatly with tug of war with a Ragger or similar.