@Livelifelaughter
Not wanting to see or hear about you is not necessarily an indicator that they disapprove of the relationship. It may just be that they have no desire to become involved in their still married father's love life. Inviting their father to Valentine's lunch with a boyfriend could well be something that they have done in the past ,and their father was free to say yes or no.
It is unreasonable to expect them to change their behavior to accommodate their father 's new relationship about which they choose to remain blind. Instead, it is up to their father to say that he is available or unavailable on Valentine's Day.
It is quite possible that they view their dad as a still married man. Consider, that they may be having what could be the calmest relationship ever with their parents in this limbo status . Their parents are living apart and not arguing. Neither parent may be suffering any financial hardship; all of the family resources remain intact, and mom and dad are living peaceful separate lives while their marriage is still in place. By not involving themselves in their parents love
lives , they can have their relationship with their parents remain essentially untouched.
This limbo status may be so comfortable for all of them that they have felt no urgency to move the divorce forward with any deliberate speed.
Your partner has been able to move his love life forward without having to split or share his assets. His ex may have an equally comfortable situation . The children have their relationships with the parents untouched by information or involvement in their parents' new relationships.
This limbo state is a win win for all with the exception of new romantic partners who envision their relationships moving to some new stage. It is quite possible that the new relationships have arrived at the intended destination.
If this destination is not your destination of choice, you might want to consider ending this relationship and seeking a legally free partner who comes without so much baggage.