Justine, if it is only to get him to socialise with other children, maybe you could try a playgroup instead? That way, he will get the social interaction with others, but you will be there with him the whole time. The first few times i took Lindsay to playgroup, he was clingy, but after a while when he saw the other kids having fun, or if there were toys he loves to play with (cars and trains), then he would wander off on his own and before he knew it, he was off playing with other kids.

I hope things work out soon for you.