Yep, it does suck...your pain is real. IMO your path is a little more challenging because your kids are old enough to understand what it is going on. It will be very hard to remain neutral and not let your children know your true feelings. Others may disagree but at the end of the day while they are old enough to understand your W is still their mother and I think some things they don't need to know. Use your discretion in what you tell them. I think you could still make things 100% worse if you put a wedge between them you and their mom.
Show them your character and the man that you are!