How does he tell kids he wants a divorce?
Before giving up on your marriage, however, I hope you will try counseling again.
Do not discuss divorce with your children unless you are definite about it and have chosen to separate. Your children certainly have noticed the dynamic between their parents through time. They will see that you have been marginalized over the years (and they have occasionally pushed you to the margins, too).
You needn't have martyred yourself for your children's activities -- and it's important that you don't present yourself as a victim.
All you need to say is, "Your mother and I have not been happy together for a long time. We love you very much, but our own relationship isn't working out."

Out East Show: Visit The Shamrock evergreen maze, Sannino Vineyard, Seven Ponds Orchard and the Warrior Ranch Foundation NewsdayTV's Doug Geed is heading 'Out East' to showcase the ultimate local spots you need to explore.