C.,
I am sure I am going to get hit hard by this one, but I feel strongly enough about it to go ahead and say it. I don't think it is in the best interest of the children to move in together with you and your boyfriend.
I realize that many people have had difficult first marriages and are reluctant to recommit, however, if you are not prepared to be this man's wife, your son probably shouldn't have to go for the ride in the relationship.
The reasons people don't get married are multifold: Finances, Can't afford the big wedding yet etc. Relaxed social mores have allowed people to selfishly pursue their own personal needs and the children have no say in the deal.
Unless you live by a stance which does not believe in the institution of marriage in general, then I would explore your motivations in this decision before exposing the children. They will emulate the relationships they see. If they do not see people who are willing to commit for better or worse than they will probably not have successful marriages themselves down the road.
Sorry if you find this offensive. It is my true opinion. Obviously you will ultimately do what is best for you and I do wish your family all the best.
J. L>