Anonymous wrote:OP here. Not a troll post. Thanks for the feedback. It's complicated. And I'm in therapy.
It is complicated. I also agree that you are getting a lot of very nasty responses that aren't helpful, but I do think it's important to realize that the situation as described is really unusual, and that your kids needs and stability need to come first.
If the kids know their co-parent as their father then how are you going to explain this to them? Do you think the co-parent will agree with the name change? I think it's very likely that legally he is considered their father no matter how you define the relationship. Do you want it in court/public records that your children have no biological relationship to him?
Bringing up the financial arrangements as a point in your favor is odd.
I think your time right now would be better spent with a plan for the next decade. At some point your children should be told the truth about their origins, but I'm not sure 8 years old is that point.