Thanks for your responses and advice. I am finding my situation a lonely place to be and reading the advice from you all has helped me at least to think that I am being logical and reasonable in my responses. my ex husband seems to be so much of the view that his relationship is normal and that the kids needs to accept it as such. Let's face it, there would be two fewer children on the planet if he had been true to his own sexuality in the first place rather than be the instigator of so much hurt and destruction. I really try to be positive with my children about them accepting him as a gay man,  but I think he is forcing it on them too quickly and I worry that the ultimate outcome could be catastrophic. So thank you just for listening.

I think you are dealing with this remarkably well. The main thing I picked out from your post was that your ex lied. That would be a big issue for me. Your daughter, who was being very generous and forgiving has been badly let down by him and I fear she may now refuse further contact. Which I have to say I would totally understand. Your ex has basically out his own desires above that of your children and that has to be made plain to him.
One thing that crops up over and over on the forum is how selfish our spouses are and this is a price example. Does your childrens school have a guidance dept that could help?

Nicci you said " I want to encourage them to have a relationship with their dad, but I feel very strongly that they should not be forced to accept his partner as part of the package."

I think before you encourage them to do anything you....you need to ask them what THEY want, and they need to know that their choices matter. And that they can confide in you.

The family unit of you & your children are, in my 
opinion.....of more importance than the man who decided that family unit wasn't what he wanted

It will be ideal if we can talk to our spouses about putting our kids first, but usually it does not happen. I wish I can talk to my GHIDSD like Wondering suggests, but it does not work like that on my end. Most likely they want us to walk their way on their terms.
They lied to us through our entire marriage/relationships putting themselves first and what I relized it won't change all of a sudden not even for kids. Those spouses really victimize themselves and think they deserve everything and that they can do anything to keep them happy.
Their EGO is priority.I often feel that odds are on their side and they get what they want even if this will cost us STRIAGHT SPOUSES emotional drainage like we were not hit enough already...it is like never ending story. You want to move on and detach and you cannot do it fully, because of their actions with our kids.
I struggle with that on my end when my GHIDSD who does whatever he wants even if we had a different agreement.
My kids are young and do not know about their father yet. Our mutual agreement was to keep that news away from them for now till we divorced and slowly we would "introduce" them to different side of daddy. But those were just words on his end...he seems to be ok to live with his boyfriend(and he claims that this has no place that he just visits him every day for long hours and have access to the house.. really? Am I 5 years old? I know you fooled me all these years, but really?!) and introduce him to our kids as his friend and have his significant around my kids like this is not harmful, because they do not know, because he does not do anything with him in front of them. I understand that eventually they will be around his partner, but Dude do this slowly. Have them familiar with having 2 houses first.
What is this then? Him living with him, having kids around and his boyfriend at the same time? Getting to know each other better? Do you really have to kiss in front of kids to say oh yes this is exposure? But if it does not happen then it is ok, it is not wrong?
We are not divorced yet. I just cannot comprehend these gay spouses thinking.
Or I am wrong? Am I?
Anyway, I made a big progress if it comes to see his true colors and I do not blame myself for what had happend in our marriage and I do not think of myself less anymore, but this constant ignorance and his position with kids drains blood of me.
Nicci,I feel for you.
You would think that since the truth is out and your kids know that it should be easier and even for your husband to become authentic, loving and compassionate parent, but it seems like it will never change. I understand he wants kids to get to know his partner, but shouldn't this happen on your kids pace? Whenever they are ready? Forcing won't resolve anything. It will do opossite.
Or maybe we STRAIGT SPOUSES do not get it?
How you can lie to your teenage girl regarding you boyfriend presence at the family event? was it more important for your husband to please his boyfriend than your own kid? Your desires are so much on demand that you cannot consider couple days with your kids only to build that band, explain someting or make those kids feel like they are the most important people, especially at their emotional stage right now?!
It makes my head to spin.
I think it is like Rob said many times at this forum, we need to keep that normal house with our kids on our time and be for our kids when they need us. But still it is painful to not have tat control and not always be able to protect our kids.