Tug of war

Question:
 My 7 month old bull terrier or boxer cross type puppy (we dont know what he is as he is a rescue dog and I have never seen anything like him) loves to play tug of war and he is very strong. Our behaviorist told us never to let him win but latly it has been very difficult for me, my brother and dad love to play it with him and he usualy ends up been dangled in the air. I have seen dogs on TV hanging on to things in this manner for minuates and the people saying they could do it for hours but I was wondering it it could harm a dog of this age. My second problem about this is I can only just manage to hang on and as his is not fully grown yet is there any way I can get him to give in or not to play it so much. If I dont play with the toy he just goes and gets something else that he cannot have and plays with that such as socks. Also he drags me across the floor if I sit down, I weight nearly 10 stone and he is only 22kg is this normal and could this indicate what type of dog this is. I have a little sister who is 5 and a newphew who is 2 that live in the house and he plays too rough with them is there any way to get him to stop he just grabs a toy and waves it in frount of them till they grab it and then he pulls them round the room until they give up, they often enjoy been draged around especially the 2 year old but I am worried about what habits we are teaching him. We are getting the trainner back in (to sort out tiolet training fully) soon but we dont know when she will be able to come she is going to ring back but any help in the mean time would be great.
Answer:
 As a behavioral consultant (and remember, anyone is the US can call themselves a behaviorist WITHOUT havign ANY formal dog work at all!!! I have known many folk calling themselves behaviorists who have FAR less dog experiences than I have - so don;t always go by what someone calls themselves - I feel a behaviorist is one who had a degree in animal behavior from an actual vet school - everyone else is a consultant or trainer...) Now, tug of war IF PLAYED BY SET RULES is a FINE game. But you need to have rules. 1) Pup may NOT play until he will take and drop the toy on verbal cue from human. 2) Human starts and stops the game. So if pup brings you the toy, he has to do some basic obedience (just a few sits, downs and stands and maybe a stay or two) before tug commenced. Game is stopped several times during play for some quick command drills. If pup has toy and refuses to let go then you STOP PLAYING AND STOP FIGHTING the pup for it. So, you, look sternly and say sternly, "GAME OVER" or whatever you choose, just be consistant with it. Now drop the toy and STALK away, ignoring the pup. If pup brings you the toy, turn and walk away a couple times. Pup cannot play by the rules, pup cannot play that game. Now, return to the pup, have a treat to trade the toy for. Tell the pup to give you the toy (I avoind lip pinhces and such as they can create a pup that is mouth fearful because the lip pinch many trainers and so called behaviorists use is based on pain and not trust and learning) and if the pup gives the toy, he gets the reward. If not, ALL DONE, and walk away. I also sit and do drills where I have my students give and take toys to reinforce human rules the toys, but we let pups play with them. Tug is a fine game if played by the rules humans set. My dogs have all been taught to play it.
Answer:
 Thanks for the reply. My pup knows how to drop, he takes a toy on command and you can put the toy on him nose without him getting it on command. The behaviourist I have for him is from a large group called Bark Busters, I think they are also in the US as they are world wide. She said to never let him win however if I do it your way how do I make sure he understands that he is not winning I just have stopped the game. We were haveing problems with him been the dominat dog (I understand that he didnt really want to but we were not doing the role propaly) and we are still working hard on it, so I dont want to confuse him anymore.