mate you might think this sounds daft, but is it not just a crush ? like something new because you have been with your missus for so long. how is your relationship with your missus, i know you said your not in love with her, but do you have a bad relationship in general, because imo, its the kids you need to think about, if you and your missus have a bad realationship, that aint good for the kids, so parting might be the rite thing to do, but if its just a case of your relationship has gone a bit stale, which most relationships do at some point, i wouldnt throw it all away for a crush.

good luck with whatever you choose.