C.S.
I think it is a wonderful idea, as long as you don't mind each other being with someone else. I think the separation is well established. Not to say that they won't ever fantasize about the two of you together, but that could happen any way.
I sometimes have a friends daughter who is a single parent. While she is with us, she sometimes calls me Mom and him Dad or sometimes it is done in talking..."Dad did it". Her Dad is so far away, she really only knows his voice. So it is possible they may think that, but they are also old enough to understand you when you say, ...at Daddy's house.