Hi Lena, 

I wrote out some thoughts about amicable divorce in a new thread so it's easy for anyone to find in the future. http://straightspouse.boardhost.com/viewtopic.php?id=774

But, let's leave your post here so that I can customize my thoughts for your specific situation:

Lena,  welcome to our family.  I'm so sorry you find yourself here.  But we welcome you and we hope that we can help you through this hard time in your life.  Know that this will just be a dark period and there are better times ahead.   You will make it!

You situation is so similar to mine.  I am also in my late 30's, had two kids and 16 years of marriage.  My ex wanted to be straight and took me along for a ride that was destined to crash.  I just wish she had told me what ride I was getting on.  She cheated on me and left me for a married woman and turned in to a monster in the process.  

Divorce is hard no matter what.  But if the two people can be reasonable and understand that turning it into a big fight will only cost everyone more money and create stress in the home and be harder on the kids, then working together and doing things amicably is a great way to move forward. 

Understand that there a few big decisions that need to be ironed out.  If you can get on the same page with these issues, then everything else can fall into place easily.  If you can't agree on the first.. then things are going to get hard. 

Issue one is kids.  Will you do joint custody or will one parent have majority time?  Will joint custody be harmful to the kids?  Will he take good care of them?  If you are a stay-at-home mom with younger kids you will have a strong case to keep majority custody.  If you both work and the kids are older then most likely you will fall somewhere in the 50/50 to 70/30 range.  Child support is typically not a negotiation because most states have a calculator that determines the amount.  You can decide to adjust that if both parties agree, but this is not very common.  Note that child support can get very expensive.  One way for the man to lower his monthly cost is to have more time with them.  Don't mistake his intentions on this. 

If you can work out custody and child support, then finances are the rest of the issue. 

Who is going to stay in the house?  Can either party afford to refinance in their own name and keep it?  Or do you have to sell it?   Or if renting, who keeps the lease and who leaves?  
Do you have a large difference in income?  If so, then you are entitled to keep some standard to living, so he will need to offer you alimony or spousal support for a period of time.. maybe forever. 
Do you have 401k, pensions, other retirement assets?  Typically this is split 50/50 between you.  
You will have to split up your debts as well as your assets.. 

If you can sit down at the kitchen table and come to a general idea of an agreement on these big things, then you can probably do it amicably.  

I also recommend consulting with a couple of attorneys to ask lots of questions.  Just meeting with them doesn't mean you have to hire them.. just getting info and learning a lot. 

Good luck.. we are here for you!