He is not going to kidnap the dcs to his parents/other & leave the country. It is hysteria
He is having these people over fairly simply: "Thanks for picking me up to take me to airport, would you like to come at 12H for a spot of lunch before we leave ?"
I think it is actually to your advantage, to be there, to show you are providing the DCs for him to say Goodbye. & showing these friends, that you have not been living with him, you are not making lunch, that you are not taking him to airport, as you are now single. (He will leave all the clearing up presumably. you could remark on it, saying anything not cleaned and put away shall be binned, You am not his cleaner.)
This will instantly be relayed by the 3rd partys to his entourage.
and yes, don't arrive too early, arrive with your kids & suitcase & start putting washing machine on around them, as he opens his M&S tapas. Do not talk to him, be polite but occupied with them.
Q "Have you been away?"
A "yes, prick & I are no longer living together, I will be finding other accom. once the finances have been settled".